Illumination device for use in endoscope

ABSTRACT

An illumination device for use in an endoscope includes a light source, an optical fiber and a wavelength conversion member. The optical fiber guides light to a tip end of an endoscope insertion portion of the endoscope. The wavelength conversion member is provided at an emission end of the optical fiber. The wavelength conversion member configured to be excited by the light source. The illumination device can provide white illumination light obtained by mixing light emitted from the optical fiber and light obtained by exciting the wavelength conversion member by the light emitted from the optical fiber. Also, the illumination device can provide illumination light being different from the white illumination light, by using other excitation light.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/478,704, filed on Jun. 4, 2009 which claims priority from JapanesePatent Application Nos. 2008-146660 (filed on Jun. 4, 2008), 2008-152932(filed on Jun. 11, 2008), 2008-155597 (filed on Jun. 13, 2008) and2008-156047 (filed on Jun. 13, 2008), the entire contents thesedocuments hereby incorporated by reference, the same as if set forth atlength.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates to an illumination device for use in an endoscope.

2. Description of the Related Art

In light source devices using a laser beam, various types of lightsource devices which obtain white light by a laser beam and visiblelight generated by a wavelength conversion member, such as a phosphorexcited by the laser beam, have been proposed. In these types of lightsource devices, a laser beam has a line spectrum in a specificwavelength region. Accordingly, a wavelength region where the emissionintensity is low may be generated over a relatively wide range aroundthe wavelength region of the line spectrum. For this reason, in normalillumination, a phosphor which emits light in a broad wavelength regionis appropriately selected in order to improve the color renderingproperties. Moreover, the wavelength region where the emission intensityis low may be compensated by adding other kinds of laser beams inaddition to the above laser beam. For example, JP 2006-173324 A(corresponding to US 2006/0152926 A and US 2008/0205477 A) describes anexample where a blue laser beam as excitation light and a laser beamhaving a different excitation wavelength from the blue laser beam areadded.

Meanwhile, in a light source device for use in the endoscope filed,illumination light for diagnosis under light in a specific wavelengthband may be required in addition to obtaining white light having highcolor rendering properties. In a technique called a spectral diagnosticsin the endoscope filed, a new blood vessel, which is generated in amucous membrane layer or an underlying layer of a mucous membrane, isobserved using the light in the specific wavelength band so as todetermine if there is cancer. Illumination light used for observationhas a larger scattering characteristic as the wavelength becomes short.Therefore, information about a relatively shallow layer can be obtainedwith a short wavelength, and information about a relatively deep layercan be obtained with a long wavelength. For this reason, in case ofobserving the surface microstructure while a deep reaching degree oflight is limited to a surface layer, it is important to make a band ofillumination light narrow in order to improve the contrast. For example,JP Hei.6-40174 A describes an endoscope for performing an illuminationoperation with light which is in a narrow wavelength band and which isextracted by using a narrow-band filter.

Moreover, for endoscopic diagnosis of an upper alimentary canal, a nasalendoscope less stressful to a patient is being used in place of aperoral endoscope. In the case of the nasal endoscope, an insertionportion is thinner than that of the peroral endoscope, and it isdifficult to secure the thickness of a light guide. Accordingly, inorder to capture a bright image, improvements are required such asincreasing an amount of illumination light or improving a sensitivity ofan imaging device.

Furthermore, also in the thin endoscope, measurement and diagnosis in anarrow band are beginning to be required. Narrow-band diagnosis isdisclosed in “Trials for development and clinical application of anelectronic endoscope system having a built-in narrow band filter (NarrowBand Imaging: NBI)” (Yasushi Sano, Shigeaki Yoshida (National CancerCenter East Hospital), Masahiko Kobayashi (Self-Defense Forces CentralHospital), GastroenterolEndosc, Sep. 20, 2000.).

Also, JP 2641653 B2 describes an electronic endoscope capable ofselecting an optimal wavelength region according to an observed body andacquiring a normal color image (visible information) with time-seriesillumination within a visible wavelength band using a solid stateimaging device provided in the tip portion of the endoscope. Theelectronic endoscope of this reference is also capable of acquiring animage with infrared light or ultraviolet light by illuminating suchlight, which includes an infrared or ultraviolet wavelength band otherthan the visible wavelength band, in a time-series manner in order toeasily detect a color tone difference of each part of the observed body,which is difficult to be distinguished in a normal image in the visibleregion, and displaying the image with desired colors assigned.Therefore, JP 2641653 B2 describes that a laser or an LED which emitslight in a narrow wavelength region is exemplified as a light source forperforming illumination using light in the narrow wavelength region.Also, JP 2641653 B2 describes that a light source being provided with anabsorption type filter in which coloring materials are mixed or avapor-deposited type filter on an emission port of a lamp which emitslight in a wide band, such as a xenon lamp, a halogen lamp, and a strobelamp in order to limit an output wavelength may also be used. Moreover,JP 2641653 B2 describes that a plurality of such light sources are usedin a wavelength region from an ultraviolet region to an infrared region.In addition, since various kinds of illumination light in apredetermined wavelength region from an ultraviolet region to aninfrared region need to be guided in JP 2641653 B2, it describes thatillumination light emitted from the light source is guided to the tip ofthe endoscope by a light guide similar as in the related art.

Thus, the endoscope for use in spectral diagnostics is requested to emitnarrow-band light while making it compact. In a light source describedin JP 2006-173324 A, in order to obtain emission of green light having anarrow bandwidth, coupling using a so-called DPSS green SHG laser bysecond harmonic generation is performed on the light source side, forexample, by using a prism. However, in this method, it is requested thata phosphor, which is excited by a blue laser beam to emit light of greento red colors do not absorb, for example, green light introduced byother laser beams. That is, as a phosphor disposed in the middle of anoptical path in order to acquire white light, there is no choice but toapply only a phosphor which rarely absorbs a laser beam for obtaininglight in a specific wavelength band other than a laser beam forgeneration of white light. Moreover, in case of performing illuminationwith such a green laser, a noise is easily superimposed on a capturedimage because of speckle (interference) or flickering easily occurs on adynamic image due to the high coherence. Moreover, it may be conceivedto eliminate the limitation of a phosphor by providing a white lightillumination optical system and an illumination optical system of aspecific wavelength band as separate optical paths. However,particularly in an endoscope, a light guide serving as an optical pathbecomes bulky. In addition, since it is necessary to provide a newirradiation window at the tip of an insertion portion, it becomesdifficult to make the insertion portion thin. Moreover, the light sourcedescribed in JP 2006-173324 A irradiates light in a visible wavelengthregion like JP Hei.6-40174 A or the non-patent document ('Trials fordevelopment and clinical application of an electronic endoscope systemwith a built-in narrow band filter (Narrow Band Imaging: NBI)').Accordingly, in order to improve the color rendering properties, thewavelength width of emitted light is made wide. Therefore, in order toacquire a narrow-band imaging signal of a blue or green color which isuseful especially for an endoscope, there still remains many problems ina combination of suitable phosphors, switching of excitation lightsources in a time-series manner, a signal calculating method, and thelike. That is, it is still difficult to precisely separate the emissionwavelength band by switching of excitation light and to make lightselectively emitted.

In the case of mounting a light emitting device, such as an LED or asemiconductor laser, in a tip portion of the endoscope, particularly inthe case of disposing a plurality of light emitting devices as describedin JP Sh.60-225820 A, it is requested to make the light emitting devicesvery small and thin. Thus, in the case of white illumination suitablefor illumination of an endoscope, for example, in the case of using awhite LED or a white laser, the illumination system may be configured bya semiconductor laser or an LED used as an excitation light source and aphosphor as described in JP 2005-205195 A and JP 2006-173324A. In thiscase, however, trade-offs between making the phosphor very large andimproving the efficiency occur. For this reason, since there waslimitation in the size of a phosphor when a light emitting device ismounted at the tip portion of the endoscope, there was also limitationin improving the efficiency.

On the other hand, infrared light and ultraviolet light other than avisible range may also be used to acquire a useful image for diagnosticimaging, especially medical image diagnosis like the endoscope describedin JP 2641653 B2. However, the endoscope apparatus described in JP2641653 B2 is an apparatus in which both light in a visible range andinfrared light or ultraviolet light other than the visible range areused by switching light having a narrow-band wavelength in a time-seriesmanner, and such light components are directly incident on a light guideto be then directly irradiated to a body to be inspected from the tip ofthe light guide, but is not an apparatus that irradiates white lightincluding plural wavelength components in a visible range. Therefore, JP2641653 B2 describes that a fiberscope which uses an optical fiber maybe used instead of the electronic endoscope which uses a light guide.However, in the technique described in JP 2641653 B2, the optical fiberis used only to guide light having many narrow-band wavelengths like alight guide. Accordingly, in the endoscope described in JP 2641653 B2,even if an optical fiber is used in place of the light guide, it was notpossible to use a white LED and a white laser, which are described in JP2005-205195 A and JP 2006-173324 A in which white light is obtained bymaking light emitted from a semiconductor laser or an LED serving as anexcitation light source incident on a light guide or an optical fiberand by coating the tip of the light guide or the optical fiber with aphosphor.

Moreover, it is assumed that as a light source of an endoscope, used isa white LED or a white laser including: a semiconductor laser or an LEDwhich emit excitation light, for example, blue excitation light; anoptical fiber which guides the excitation light; and a phosphor providedat the tip of an optical fiber and excited by excitation light asdescribed in JP 2005-205195 A and JP 2006-173324 A and that an infraredemitting device which is useful in medical fields and emits infraredlight other than a visible range like the endoscope described in JP2641653 B2. In this case, the infrared light could not be efficientlyguided in the related art because the optical fiber which guides theexcitation light is configured to efficiently guide the excitationlight. In addition, in the case of a phosphor for use in the known whiteLED or white laser, there was a problem that the infrared light waswavelength-converted into fluorescent light.

For this reason, in a light source device of the related art for anendoscope, excitation light and infrared light are guided using separateoptical fibers. An endoscope apparatus using such a light source devicefor an endoscope is shown in FIG. 32. As shown in FIG. 32, an endoscopeapparatus 400 has an endoscope device 402 and a control device 404. Theendoscope device 402 is configured to include an insertion portion 406,an operating section 408, a main body operating section 410, and aconnection portion 412. The insertion portion 406 is configured to havea flexible soft portion 414, a bending portion 416, and a tip portion418. A phosphor portion 420, an irradiation port 422 for illuminationlight, an objective lens (not shown), and a CCD 424 are provided in thetip portion 418 of the insertion portion 406. Moreover, the controldevice 404 includes a blue laser diode (hereinafter, referred to as anLD) 426 and an infrared LD 428, which serve as light sources ofexcitation light, a light source controller 430 that controls the blueLD 426 and the infrared LD 428 to emit light in a time-series manner,and a processor 432.

In addition, two optical fibers 434 and 436 and one scope cable 438 areinserted inside the endoscope device 402. The optical fibers 434 and 436are inserted in the endoscope device 402. One ends of the optical fibers434 and 436 are connected to the blue LD 426 and the infrared LD 428 ofthe control device 404, respectively, and the other ends extend to thetip portion 418 of the endoscope device 402. In the tip portion 418 ofthe endoscope device 402, the tip of the optical fiber 434 extends tothe position of the phosphor portion 420 so that blue light from theblue LD 426 is incident on the phosphor portion 420 and is then emittedfrom the irradiation port 422 as white light (or pseudo white light)that becomes illumination light. The tip of the optical fiber 436extends to the irradiation port 422 so that infrared light from theinfrared LD 428 is emitted from the irradiation port 422. In addition,the scope cable 438 is a cable for transmission of an imaging signal.One end of the scope cable 438 is connected to the processor 430 of thecontrol device 404, and the other end is connected to the CCD 424. Theprocessor 430 converts the imaging signal transmitted from the CCD 424into a video signal and supplies the video signal to a monitor (notshown).

Here, the blue LD 426, the infrared LD 428, the two optical fibers 434and 436, and the phosphor portion 420 form a light source device 440.Details of the light source device 440 are shown in FIG. 33. As shown inFIG. 33, a collimator lens 442 is disposed between the blue LD 426 andthe optical fiber 434, and an illumination optical member 446 to whichthe phosphor portion 420 is attached is provided at the tip of theoptical fiber 434, which is held by a holding end portion 444. Inaddition, a collimator lens 448 is disposed between the infrared LD 428and the optical fiber 436, and a concave lens 450 is provided at the tipof the optical fiber 436. In the light source device 440 of the relatedart, infrared light from the infrared LD 428 is independently guided bythe optical fiber 436. Therefore, the concave lens 450 is needed at thetip of the optical fiber in order to increase the divergence angle ofthe infrared light.

In the case where, like this light source device 440, a white laserconfigured to include the blue LD 426, the optical fiber 434, and thephosphor portion 420 are used as an observation light source, if theinfrared LD 428 is used together as an observation light source formaking observation under the infrared light that is effective in themedical field, the dedicated optical fiber 436 which guides the infraredlight and is different from the optical fiber 434 guiding blueexcitation light from the blue LD 426 needs to be used. However, theresultant device configuration is complicated, and it is difficult toreduce a size of the device. In addition, emission positions of whitelight and infrared light are not identical. Therefore, for example, whennormal images under the white light and images under the infrared lightare acquired in a time-series manner and displayed, a difference betweenimages and/or appearance of a shadow would be conspicuous. Therefore, itis difficult to compare the images.

Moreover, in the case where an infrared emission LED device is used tomake observation under infrared light that is effective in the medicalfield, even if a white (or pseudo white) LED formed of a blue LED deviceand a phosphor and an infrared emission LED device are integrated as alight source device for an endoscope, it is necessary to seal the whiteLED and the infrared emission LED device. Such a light source device foran endoscope is shown in FIG. 34. As shown in FIG. 34, a light sourcedevice 460 includes: a common substrate 464 formed with two recesses 462and 463 separated by a separation barrier 461; a blue LED device 468fixed to the recess 462 by an adhesive 466; a resin sealing portion 470,which seals the blue LED device 468 provided in the recess 462, in asealing region with a phosphor-containing resin in which a phosphor ismixed; an infrared emission LED device 472 fixed to the recess 463 ofthe common substrate 464 by an adhesive; and a resin sealing portion474, which seals the infrared emission LED device 472 provided in therecess 463, in a sealing region with a resin in which a phosphor is notmixed, the resin sealing portion 474 which allows infrared light totransmit therethrough. Here, the blue LED device 468 and the resinsealing portion 470 formed of the phosphor-containing resin form a white(or pseudo white) LED, and white light (or pseudo white light) isemitted from the resin sealing portion 470. In addition, the infraredemission LED device 472 emits infrared light through the resin sealingportion 474.

In the case where, like this light source device 460, a white LEDincluding the blue LED device 468 and the resin sealing portion 470formed of the phosphor-containing resin is used as an observation lightsource, if the infrared LED 472 is used together as an observation lightsource for making observation under the infrared light that is effectivein the medical field, it is necessary to use a resin in which a phosphoris not mixed for sealing the infrared LED 472, while it is necessary tomix the phosphor, which is excited by blue excitation light from theblue LED device 468 and converts wavelength into white light (or pseudowhite light), in a resin for sealing the blue LED device 468, while aresin in which a phosphor is not mixed needs to be used as a resin forsealing the infrared emission LED device 472. Therefore, it would bedifficult to achieve efficient white illumination and to reduce a sizeof the device. In addition, since emission sources of white light andinfrared light are not identical, for example, when normal images underthe white light and images under the infrared light are acquired in atime-series manner and displayed, a difference between images and/or adifference in appearance of shadows are conspicuous. Therefore, it isdifficult to compare both the images.

SUMMARY

The invention provides an illumination device for use in an endoscopethat mixes light emitted from an optical fiber and light obtained byexciting a wavelength conversion member by the light emitted from theoptical fiber for irradiation as while illumination light.

According to a first aspect of the invention, an illumination device foruse in an endoscope includes a light source, an optical fiber and awavelength conversion member. The optical fiber guides light to a tipend of an endoscope insertion portion of the endoscope. The wavelengthconversion member is provided at an emission end of the optical fiber.The wavelength conversion member configured to be excited by the lightsource. Light emitted from the optical fiber and light obtained byexciting the wavelength conversion member by the light emitted from theoptical fiber are mixed to generate white illumination light.

Also, the light guided through the optical fiber may have differentplural wavelengths. The wavelength conversion member may be disposed atthe tip end of the endoscope insertion portion and is separately excitedby the light of the respective wavelengths.

Also, the illumination device may further include a light emittingdevice that is provided at the tip of the endoscope insertion portionand emits light in a visible wavelength band.

Also, the illumination device may further include an illumination lightcontrol unit that alternately switches between illumination with thewhite light and illumination including light in a specific visiblewavelength band, every imaging frame of an imaging device of theendoscope.

Also, the light source may include a first light source and a secondlight source. The first light source that emits a laser beam having afirst wavelength as a center wavelength. The second light source emitsan infrared laser beam having a second wavelength included in aninfrared wavelength band as a center wavelength. The wavelengthconversion member may include a first wavelength conversion member and asecond wavelength conversion member. The first wavelength conversionmember is configured to be excited by the laser beam of the first lightsource to emit light. The second wavelength conversion member isconfigured to be excited by the infrared laser beam of the second lightsource to emit light that is in a specific visible wavelength band andis shorter than the second wavelength. A band width of the light emittedby the second wavelength conversion member is narrower than asubstantial sensitive wavelength band, for a specific detection colorcorresponding to the light emitted by the second wavelength conversionmember, of an imaging device.

Also, the light source may include a first light source and a secondlight source. The first light source emits a laser beam having a firstwavelength as a center wavelength. The second light source emits aninfrared laser beam having a second wavelength included in an infraredwavelength band as a center wavelength. The wavelength conversion membermay include a first wavelength conversion member and a second wavelengthconversion member. The first wavelength conversion member is configuredto be excited by the laser beam of the first light source to emit light.The second wavelength conversion member is configured to be excited bythe infrared laser beam of the second light source to emit light that isin a specific visible wavelength band and is shorter than the secondwavelength. The light, which that the second wavelength conversionmember is excited by the infrared laser beam of the second light sourceto emit, may be in a wavelength band of 530 nm to 570 nm.

Also, the light source may include a first light source and a secondlight source. The first light source emits light having a firstwavelength. The second light source emits light having a secondwavelength different from the first wavelength. The wavelengthconversion member may be configured to be excited by the light of thefirst light source to emit first fluorescence having a wavelengthdifferent from the first wavelength. An energy of fluorescence of thewavelength conversion member when the wavelength conversion member isexcited by light having the second wavelength and having a certainenergy may be equal to or less than 1/10 of that of fluorescence of thewavelength conversion member when the wavelength conversion member isexcited by light having the first wavelength and having the certainenergy. Also, the energy of the fluorescence of the wavelengthconversion member when the wavelength conversion member is excited bythe light having the second wavelength and having the certain energy maybe equal to or less than 1/100 of that of the fluorescence of thewavelength conversion member when the wavelength conversion member isexcited by the light having the first wavelength and having the certainenergy.

Also, the energy of the fluorescence of the wavelength conversion memberwhen the wavelength conversion member is excited by the light having thesecond wavelength and having the certain energy may be equal to or lessthan 1/10,000 of that of the fluorescence of the wavelength conversionmember when the wavelength conversion member is excited by the lighthaving the first wavelength and having the certain energy.

Also, the wavelength conversion member may be an up-conversion materialincluding oxide-fluoride-based crystallized glass.

Also, the wavelength conversion member may include a down-conversionmaterial that emits green light by excitation.

Also, the wavelength conversion member may include a down-conversionmaterial that emits blue light by excitation.

The invention may provide: an illumination device for use in anendoscope that can selectively irradiate either white light, which isgenerated to include a laser beam and luminescence of a phosphor, orlight in a specific narrow visible wavelength band with a simpleconfiguration while achieving its compact configuration; and anendoscope apparatus including the illumination device.

(1) According to a second aspect of the invention, a light source deviceincludes a first light source, an optical fiber, a first wavelengthconversion member, a second light source, an optical coupling unit and asecond wavelength conversion member. The first light source emits alaser beam having a first wavelength as a center wavelength. The laserbeam of the first light source is incident on a light indent side of theoptical fiber and is transmitted through the optical fiber. The firstwavelength conversion member is disposed on a light emission side of theoptical fiber and is excited by the laser beam of the first light sourceto emit luminescence. The laser beam of the first light source and theluminescence from the first wavelength conversion member are mixed toobtain while light. The second light source emits an infrared laser beamhaving a second wavelength included in an infrared band as a centerwavelength. The optical coupling unit introduces the infrared laser beamof the second light source to an optical path on the light incident sideof the optical fiber. The second wavelength conversion member isdisposed anterior to the light incident side of the optical fiber on theoptical path. The second wavelength conversion member is excited by theinfrared laser beam to emit luminescence which is in a specific visiblewavelength band and which is shorter than the second wavelength. Eitherof the white light or the luminescence in the specific visiblewavelength band is emitted selectively, or both of the white light andthe luminescence in the specific visible wavelength band are emittedsimultaneously.

With this light source device, the optical coupling unit causes anillumination optical system based on the first light source and anillumination optical system based on the second light source to becoaxial, and the first wavelength conversion member and the secondwavelength conversion member are disposed anterior to the light incidentside of the optical fiber on the optical path. Thereby, the luminescencecaused by the laser beam from the first light source is obtained fromthe first wavelength conversion member, and the luminescence caused bythe laser beam from the second light source is obtained from the secondwavelength conversion member. As a result, since the white light isacquired by a part of the laser beam from the first light source and theluminescence from the first wavelength conversion member, and theluminescence in the specific visible wavelength band is obtained byexciting by the infrared laser beam from the second light source.Therefore, either the white light or the luminescence in the specificvisible wavelength band can be emitted selectively with the simpleconfiguration.

(2) In the light source device of (1), the second wavelength conversionmember may be disposed anterior to the first wavelength conversionmember on the optical path.

With this light source device, since the second wavelength conversionmember is disposed anterior to the first wavelength conversion member onthe optical path, the luminescence from the first wavelength conversionmember is transmitted through the second wavelength conversion memberwhile diffusing through the second wavelength conversion member. As aresult, the white light is emitted while being diffused. Moreover, thelaser beam of the second light source is transmitted through the secondwavelength conversion member without loss while exciting the secondwavelength conversion member to emit the luminescence in the specificwavelength band. The white light and the luminescence are emittedfrontward on the optical path.

(3) In the light source device of (1), the second wavelength conversionmember may be formed to be included in a light guiding material of theoptical fiber.

With this light source, the optical fiber functions as the secondwavelength conversion member since the optical fiber includes the lightguiding material that is excited by the infrared laser beam to emit theluminescence, which is in the specific visible wavelength band and whichis shorter than the second wavelength. Accordingly, since the secondwavelength conversion member does not need to be disposed on the lightemission side of the optical fiber, the further compact configurationcan be realized.

(4) In the light source device according to any one of (1) to (3), thesecond wavelength conversion member may be an up-conversion materialincluding oxide-fluoride-based crystallized glass.

With this light source, the luminescence in a narrow band of green canbe obtained particularly by the light in the infrared wavelength band.

(5) According to a third aspect of the invention, an endoscope apparatusincludes the light source device according to any one of (1) to (4), anendoscope and a control unit. The endoscope includes an illuminationoptical system and an imaging optical system. In the illuminationoptical system, the light emission side of the optical fiber of thelight source device is disposed at a tip side of an endoscope insertionportion so as to illuminate a body to be inspected. The imaging opticalsystem includes an imaging device that receives light from the body tobe inspected and outputs an imaging signal. The control unit causes thewhite light and the luminescence in the specific visible wavelength bandto be emitted simultaneously or causes either the white light or theluminescence in the specific visible wavelength band to be emittedselectively.

With this endoscope apparatus, the endoscope insertion portion can bemade thin. Also, the white light or the luminescence in the specificvisible wavelength band can be controlled to be selectively emitted asirradiated light. As a result, the spectral diagnostics can be performedeasily.

(6) In the endoscope apparatus of (5), a wavelength width of thespecific visible wavelength band in which the second wavelengthconversion member emits the luminescence is narrower than a substantialeffective sensitivity wavelength band, for a specific detection colorcorresponding to the luminescence, of the imaging device.

With this endoscope apparatus, the second wavelength conversion memberemits the luminescence, which is in the wavelength band narrower thanthe substantial effective sensitivity wavelength band, for the specificdetection color corresponding to the luminescence, of the imagingdevice. Therefore, there is no influence of color mixture and the like.Moreover, since region information about the invasion depth of the lightwhich is one of the observation purposes can be acquired more reliably,the contrast of an obtained image can be increased in accordance withthe observation purpose.

According to the light source device of any one of (1) to (4), either(i) white light, which is formed to include a laser beam andluminescence from a phosphor, or (ii) light in a specific narrow visiblewavelength band can be selectively irradiated with the simpleconfiguration. Moreover, according to the endoscope apparatus of any oneof (5) to (6) using the light source device, the endoscope insertionportion can be made thin by simplifying the illumination optical system,and light irradiation can be performed by controlling either of thewhite light or the light in the specific visible wavelength band to beselectively emitted. As a result, spectral diagnostics and the likeusing the endoscope can be performed easily.

The invention may provide: an illumination device for use in anendoscope that can selectively irradiate either white light, which isgenerated to include a laser beam and luminescence of a phosphor, orlight in a specific narrow visible wavelength band with a simpleconfiguration while achieving its compact configuration; an endoscopeapparatus including the illumination device; and an image processingmethod.

(7) According to a fourth aspect of the invention, a light source deviceincludes a first light source, an optical fiber, a first wavelengthconversion member, a second light source, an optical coupling unit and asecond wavelength conversion member. The first light source emits afirst laser beam having a first wavelength as a center wavelength. Thefirst laser beam is incident on a light incident side of the opticalfiber and is transmitted through the optical fiber. The first wavelengthconversion member is disposed on a light emission side of the opticalfiber. The first wavelength conversion member includes at least one kindof phosphor that emits luminescence upon excitation by the first laserbeam. The first laser beam and the luminescence from the firstwavelength conversion member are mixed to obtain white light. The secondlight source emits a second laser beam having a second wavelength, whichis shorter than the first wavelength, as a center wavelength. Theoptical coupling unit introduces the second laser beam to an opticalpath on the light incident side of the optical fiber. The secondwavelength conversion member is disposed anterior to the light emissionside of the optical fiber on the optical path and emits luminescencewhich is in a specific visible wavelength band and which is longer thanthe second wavelength, upon excitation by the second laser beam.

With this light source device, the optical coupling unit causes anillumination optical system based on the first light source and anillumination optical system based on the second light source to becoaxial. The first wavelength conversion member and the secondwavelength conversion member are disposed on the light emission side ofthe optical fiber. Thereby, the luminescence caused by the laser beamfrom the first light source is obtained from the first wavelengthconversion member, and the luminescence caused by the laser beam fromthe second light source is obtained from the second wavelengthconversion member. That is, the white light is obtained by a part of thefirst laser beams and the luminescence from the first wavelengthconversion member, and the luminescence in the specific visiblewavelength band is obtained by exciting by the infrared laser beam fromthe second light source. Therefore, either the white light or theluminescence in the specific visible wavelength band can be emittedselectively with the simple configuration.

(8) In the light source device of (7), the second wavelength conversionmember may be excited by the first laser beam to emit luminescence.

With this light source device, the second wavelength conversion member,which is configured to be excited by the second laser beam to emit theluminescence, is also configured to be excited by the first laser beamto emit the luminescence. Therefore, light components which can beemitted from the light source device are increased. As a result, thelight use efficiency can be improved. Moreover, since the combination ofemitted light can be made in various ways, the degree of freedom ofdesign at the time of light detection can be improved.

(9) The light source device of any one of (7) to (8) may further includea wavelength conversion member. In the wavelength conversion member, thefirst and second wavelength conversion members are integrated in a statewhere phosphors thereof are distributed or the first and secondwavelength conversion members are laminated integrally.

With this light source device, the device size can be reduced becausethe wavelength conversion members are integrated. In addition, theluminescence caused by the first laser beam and the luminescence causedby the second laser beam are generated from the phosphors of the firstand second wavelength conversion members, which are integrated, and areemitted frontward on the optical path.

(10) in the light source device of any one of (7) to (9), the secondwavelength conversion member may include a down-conversion materialwhich is excited to emit green light.

With this light source device, since the second wavelength conversionmember emits green light, the green light can be supplied whenperforming spectral diagnostics of an endoscope, for example.Accordingly, illumination light corresponding to the diagnostic purposecan be obtained.

(11) In the light source device of any one of (7) to (10), the secondwavelength conversion member includes a down-conversion material whichis excited to emit blue light.

With this light source device, since the second wavelength conversionmember emits blue light, the blue light can be supplied when performingspectral diagnostics of an endoscope, for example. Accordingly,illumination light corresponding to the diagnostic purpose can beobtained. Moreover, a pseudo color image for spectral diagnostics may begenerated by making the blue light emitted together with green light.

(12) According to a fifth aspect of the invention, an endoscopeapparatus includes the light source device of any one of (7) to (11), anendoscope, and a control unit. The endoscope includes an illuminationoptical system and an imaging optical system. In the illuminationoptical system, a light emission portion of the optical fiber of thelight source device is disposed at a tip side of an endoscope insertionportion so as to illuminate a body to be inspected. The imaging opticalsystem includes an imaging device which receives light from the body tobe inspected and outputs an imaging signal. The control unit controlsemission of laser beams from the first and second light sources.

With this endoscope apparatus, the endoscope insertion portion can bemade thin. Also, the white light and the luminescence in the specificvisible wavelength band can be controlled to be selectively emitted asirradiated light. Therefore, the spectral diagnostics can be performedeasily.

(13) The endoscope apparatus of (12) may further include a first memory,a second memory and an imaging image display unit. The first memorystores an imaging signal imaged under illumination light of the whitelight generated by the first light source. The second memory stores animaging signal imaged under illumination light including theluminescence, which is in the specific visible wavelength band and isgenerated by the second light source. The imaged image display unitdisplays the imaging signals, which are stored in the first and secondmemories, in different display regions, respectively.

With this endoscope apparatus, the imaging signals are stored in thedifferent memories according to a type of illumination light. Theimaging signals of the memories are displayed in the different displayregions, respectively. Accordingly, for example, an observed image underillumination light based on the white light and an observed image underillumination light based on the luminescence in the specific visiblewavelength band can be displayed separately. As a result, it is possibleto perform diagnosis while comparing the normal observed image with theimage observed in the specific wavelength.

(14) In the endoscope apparatus of (13), the control unit mayalternately switch between illumination with the white light andillumination including the luminescence in the specific visiblewavelength band, every imaging frame of the imaging device.

With this endoscope, by alternately imaging an image under illuminationof the white light and an image under illumination including theluminescence in the specific visible wavelength band, the both imagescan be acquired approximately at the same time. Accordingly, two typesof image information can be simultaneously displayed in real time.

(15) In the endoscope apparatus of any one of (12) to (14), the imagingdevice may include a color filter for detecting a specific detectioncolor component. A full width of an emission spectrum curve of thespecific visible wavelength band in which the wavelength conversionmember is excited to emit the luminescence at half maximum the emissionspectrum curve is narrower than a full width of a spectral sensitivitycurve of a wavelength band in which the specific detection color of thecolor filter is detected, at half maximum of the spectral sensitivitycurve.

With this endoscope apparatus, the full width of the specific visiblewavelength band in which the wavelength conversion member is excited toemit the luminescence at the half maximum of the specific visiblewavelength is set to be narrower than the full width of the detectionwavelength band of the color filter at the half maximum of the detectionwavelength band of the color filter. Thereby, the luminescence isdetected in a corresponding wavelength band, and the other wavelengthbands are not influenced. Accordingly, there is no influence of colormixture and the like. Moreover, since it becomes easy to adjust theinvasion depth of light with respect to a region to be observed,information from a layer to be observed can be reliably acquired, andthe contrast of an imaged image can be improved.

(16) According to a sixth aspect of the invention, an image processingmethod for use in the endoscope apparatus of any one of (12) to (15)images a frame image, which is configured to include plural detectioncolor screens on which light components in different specific wavelengthbands are detected, multiple times, and irradiates light from pluraltypes of light sources under different conditions in synchronizationwith an imaging timing of each frame image. The method includes imagingfirst and second frame images repeatedly, wherein an observed image whena body to be inspected is illuminated by the first light source isreferred to as the first frame image, and an observed image when thebody to be inspected is illuminated by the second light source isreferred to as the second frame image. The method also includesperforming a calculation process for brightness information of aspecific detection color screen of the first frame image and brightnessinformation of a specific detection color screen of the second frameimage so as to analytically acquire an observed image under light of thespecific wavelength component from the light source device.

With this image processing method for use in the endoscope apparatus,the observed image under light of a desired wavelength component can beselectively extracted by performing the calculation process forinformation of the detection color screens of the first and second frameimages in combination. That is, the observed image under the light ofthe specific wavelength component, which cannot be directly obtainedfrom a frame image obtained by single imaging can be analyticallyacquired by using frame images before and after the time axis.

(17) In the image processing method for use in the endoscope apparatusof (16), the observed image under the light of the specific wavelengthcomponent includes at least an observed image under emission lighthaving a narrow wavelength bandwidth.

With this method, since an observed image under a light component in anarrow wavelength band is analytically obtained, the invasion depth islimited to a narrow range, for example, when observing a blood vessel orgland tube structure. As a result, an image with higher contrast can beobtained.

(18) In the method of any one of (16) to (17), the observed image underthe light of the specific wavelength component includes at least anobserved image under emission light having a wide wavelength bandwidth.

With this method, since an observed image under a light component havinga wide wavelength bandwidth is analytically acquired, it is possible toobtain an image under white illumination with higher color renderingproperties.

(19) In the method of any one of (16) to (18), the observed image underthe light of the specific wavelength component is converted into aspecific color tone to generate a pseudo color image.

With this method, a capillary vessel, a gland tube structure, and thelike of a tissue surface can be highlighted, an observed object can beeasily checked, which can improve the diagnostic precision.

According to the light source device of any one of (7) to (11), either(i) white light, which is formed to include a first laser beam andluminescence from a phosphor, or (ii) light in a specific narrow visiblewavelength band can be selectively irradiated with the simpleconfiguration. Moreover, according to the endoscope apparatus of any oneof (12) to (15) using the light source device, the endoscope insertionportion can be made thin since the illumination optical system becomessimple. In addition, since light irradiation can be performed bycontrolling either the white light or the light in the specific visiblewavelength band to be selectively emitted, spectral diagnostics and thelike using the endoscope can be performed easily. Moreover, according tothe image processing method of any one of (16) to (19), an observedimage under light of a specific wavelength component which cannot bedirectly detected can be analytically acquired by using frame imagesbefore and after the time axis.

Also, the invention may provide: an endoscope apparatus that can makeobservation by selectively irradiating either white light or light in aspecific narrow visible wavelength band with the simple configurationwhile making a diameter of an endoscope insertion portion small andsuppressing heat emission of an LED device disposed at the tip of theendoscope insertion portion; and an image processing method that canperform spectral diagnostics more precisely based on image informationfrom provided the endoscope apparatus.

(20) According to a seventh aspect of the invention, an endoscopeapparatus includes a first light source, an optical fiber, a wavelengthconversion member, a first illumination optical system and a secondillumination optical system. The first light source emits a laser beam.The laser beam is incident on a light incident side of the optical fiberand is transmitted toward a tip of an endoscope insertion portionthrough the optical fiber. The wavelength conversion member is disposedon a light emission side of the optical fiber and includes at least onetype of phosphor that is excited by the laser beam to emit luminescence.The first illumination optical system mixes the laser beam and theluminescence from the wavelength conversion member to emit white lightfrom the tip of the endoscope insertion portion. The second illuminationoptical system is disposed at the tip of the endoscope insertion portionand includes a light emitting device that emits light in a specificvisible wavelength band.

With this endoscope apparatus, the laser beam from the first lightsource is guided by the optical fiber and is then irradiated to thewavelength conversion member disposed the emission end of the opticalfiber, thereby exciting the wavelength conversion member to emit theluminescence. As a result, the white light is generated by the originallaser beam from the first light source and the luminescence, whichrealizes an optical system for white light illumination. Moreover, sincethe second illumination optical system having the light emitting device,which emits the light in the specific visible wavelength band, isprovided, either white light illumination or illumination with the lightin the specific visible wavelength band can be emitted selectively withthe simple configuration. In addition, since the white illuminationlight is generated by using the laser beam, high-brightness light isobtained. In addition, since the light is guided by the optical fiber,the endoscope insertion portion can be made thin.

(21) In the endoscope apparatus of (20), the light emitting device ofthe second illumination optical system may include an LED device.

With this endoscope apparatus, high-efficiency and high-brightness lightcan be obtained. Moreover, since the laser beam of the firstillumination optical system is used together, the light amount of theLED device from the tip of the endoscope insertion portion can becontrolled. As a result, the tip of the endoscope insertion portion canbe made small, and the heat emission can be controlled.

(22) In the endoscope apparatus of any one of (20) to (21), the secondillumination optical system may include plural light emitting devicesthat emit light in different center wavelengths.

With this endoscope apparatus, various types of illumination light canbe emitted by providing the plural light emitting devices.

(23) In the endoscope apparatus of any one of (20) to (22), the secondillumination optical system may include at least a light emitting devicethat emits green light.

With this endoscope apparatus, an emphasized image can be generated inspectral diagnostics by emitting the green light.

(24) In the endoscope apparatus of any one of (20) to (23), the secondillumination optical system may include at least a light emitting devicethat emits blue light.

With this endoscope apparatus, an emphasized image can be generated inspectral diagnostics by emitting the blue light.

(25) In the endoscope apparatus of any one of (20) to (24), the secondillumination optical system may include at least light emitting devicesthat emit red light or infrared light.

With this endoscope apparatus, so-called infrared observation in whichobservation is made in a state where a drug easily absorbing infraredlight is injected into the vein can be executed by emitting the redlight or the infrared light.

(26) The endoscope apparatus of any one of (20) to (25) may furtherinclude an imaging unit and an illumination light control unit. Theimaging unit includes an imaging device that receives light from anobserved part through an observation window provided at the tip of theendoscope insertion portion and outputs an imaging signal. Theillumination light control unit switches between white light from thefirst illumination optical system and the light in the specific visiblewavelength band from the second illumination optical system, forillumination.

With this endoscope apparatus, the endoscope insertion portion can bemade thin, and the white light and the light in the specific visiblewavelength band can be controlled to be selectively emitted asirradiated light. Therefore, the spectral diagnostics and the like canbe performed easily.

(27) The endoscope apparatus of (26) may further include a first memory,a second memory and an imaged image display unit. The first memorystores an imaging signal imaged under illumination with the white lightby the first illumination optical system. The second memory stores animaging signal imaged under illumination including the light in thespecific visible wavelength band by the second illumination opticalsystem. The imaged image display unit displays the imaging signals,which are stored in the first and second memories, in different displayregions, respectively.

With this endoscope apparatus, imaging signals are stored in differentmemories according to the type of illumination light, and the imagingsignals of the memories are displayed in the different display regions,respectively. Thereby, for example, an observed image under illuminationwith the white light and an observed image under illumination with thelight in a specific visible wavelength band can be displayed separately.As a result, it is possible to perform diagnosis while comparing anormal observed image with an image observed with the light in thespecific wavelength.

(28) In the endoscope apparatus of (27), the illumination light controlunit may alternately switches between illumination of the white lightand illumination including the light in the specific visible wavelengthband, every imaging frame of the imaging device.

With this endoscope, by alternately imaging an image under illuminationwith the white light and an image under illumination including the lightin the specific visible wavelength band, both the images can be acquiredapproximately at the same time. Accordingly, two types of imageinformation can be simultaneously displayed in real time.

(29) In the endoscope apparatus according to any one of (26) to (28),the imaging device may include a color filter for detecting a specificdetection color component. A full width of an emission spectrum curve ofthe specific visible wavelength band in which the light emitting deviceemits light, at half maximum of the emission spectrum curve, is smallerthan a full width of a spectral sensitivity curve of a wavelength bandin which the specific detection color of the color filter is detected,at half maximum of the spectral sensitivity curve.

With this endoscope apparatus, the full width of the specific visiblewavelength band in which the light emitting device emits light, at thehalf maximum thereof, is set to be narrower than the full width of thedetected wavelength band of the color filter, at the half maximumthereof. Thereby, the emission light of the light emitting device isdetected within a peak of one corresponding wavelength band detection,and the other wavelength bands are not influenced. Accordingly, there isno influence of color mixture and the like. Moreover, since it becomeseasy to adjust the invasion depth of light with a region to be observed,information from a layer to be observed can be reliably acquired and thecontrast of an imaged image can be improved.

(30) According to an eighth aspect of the invention, an image processingmethod for use in the endoscope apparatus of any one of (26) to (29)includes imaging a frame image which is configured to include pluraldetection color screens on which light components in different specificwavelength bands are detected, multiple times and irradiating light froma plurality of types of light sources under different conditions insynchronization with an imaging timing of each frame image. The methodfurther includes: imaging first and second frame images repeatedlywherein an observed image when a body to be inspected is illuminated bythe first light source is referred to as the first frame image and anobserved image when the body to be inspected is illuminated by thesecond light source is referred to as the second frame image; andcombining brightness information of a specific detection color screen ofthe first frame image with brightness information of a specificdetection color screen of the second frame image so as to analyticallyacquire an observed image under light of the specific wavelengthcomponent from the light source device.

With this image processing method for use in the endoscope apparatus, anobserved image under light of a desired wavelength component can beselectively extracted by combining information of the detection colorscreens of the first and second frame images. That is, an observed imageunder the light of the specific wavelength component which cannot bedirectly obtained from a frame image obtained by performing singleimaging can be analytically acquired by using frame images before andafter the time axis.

(31) In the image processing method of (30), the observed image underthe light of the specific wavelength component may include at least anobserved image under emitted light having a narrow wavelength bandwidth.

With this method, since an observed image under the light component inthe narrow wavelength band is analytically acquired, the invasion depthis limited to a narrow range, for example, when observing a blood vesselor gland tube structure. As a result, an image with higher contrast canbe obtained.

(32) In the image processing method of (30), the observed image underthe light of the specific wavelength component may include at least anobserved image under emitted light having a wide wavelength bandwidth.

With this image processing method, since an observed image under lightcomponent having the wide wavelength bandwidth is analytically acquired,it is possible to obtain an image under white illumination with highercolor rendering properties.

(33) In the image processing method of any one of (30) to (32), theobserved image under the light of the specific wavelength component maybe converted into a specific color tone to generate a pseudo colorimage.

With this image processing method, a capillary vessel and a gland tubestructure of a tissue surface can be emphasized, and an observed objectcan be easily checked, which can improve the diagnostic precision.

According to the endoscope apparatus of any one of (20) to (29), theendoscope insertion portion can made thin, heat emission of the LEDdevice disposed at the tip of the endoscope insertion portion can besuppressed, and observation can be performed by selectively irradiatingeither white light or light in a specific narrow visible wavelength bandwith the simple configuration. In addition, according to the imageprocessing method of any one of (31) to (33), highly precise spectraldiagnostics can be performed based on image information from theendoscope apparatus.

Also, the invention may provide: a low-cost light source device that cancoaxially guide two types of emission light having differentwavelengths, has a small size, has a small diameter and is used forvarious purposes; and an endoscope system including this light sourcedevice.

Furthermore, the invention may provide: a light source device that canrealize efficient white illumination, has a small size, can makeemission sources of white light and infrared light almost the same orguide the white light and the infrared light coaxially so that theemission positions thereof can be made almost the same, for example, andcompare both images easily while decreasing a difference between theimages and/or appearance of shadows even if the normal image under thewhite light and the image under the infrared light are acquired in atime-series manner and are displayed; and an endoscope apparatus usingthe light source device.

In order to achieve the above-described objects, the inventors studied alight source device that can realize efficient white illumination, has asmall size and can make light emitting sources of white light andinfrared light or the emission positions almost the same, for making anobservation using white light and also for making an observation usinginfrared light (infrared ray) which was useful in the medical field, wasused in imaging using absorption of hemoglobin, a difference insaturation of oxygen, and the like, and could be used for diagnosis. Asa result, the inventors found out that even if blue light is guided byan optical fiber and is converted into white light by a phosphordisposed at a tip end of the optical fiber for illumination as in thewhite laser described in JP 2005-205195 A, emission positions of thewhite light and the infrared light can be made substantially the same byguiding emission light, such as the red light or the infrared light,which passes through a used phosphor without little exciting thephosphor, to the phosphor provided at the tip end of the optical fiberand by providing a light source, such as an infrared LD, which emits thered light or the infrared light, below the phosphor.

Also, the inventors found out that in a light source that obtainsdesired white color based on (i) excitation light and (ii) fluorescenceemitted from a phosphor excited by an a light emitting device ofultraviolet light to blue light, such as an LED, light emitting sourcescould be made substantially the same by arranging the infrared elementbelow the phosphor. Furthermore, the inventors found out that thisconfiguration could realize the efficiency of white illumination andminiaturization. As a result, the inventors found out that a differencebetween the images or appearance of shadows was small and thatcomparison between both the images could be easily made when a normalimage under white light and an image under infrared light were acquiredin a time-series manner and displayed.

The white laser described in JP 2006-173324 A includes a semiconductorlaser for emitting red light or infrared light which does not excite aphosphor but has a good condensing efficiency to an optical fiber andguides through the optical fiber the laser beam to the phosphor disposedat the tip end of the optical fiber, rather than inputting blue light orultraviolet light as excitation light of the white laser as described inJP 2005-205195 A. The inventors found out that, by appropriatelyselecting a phosphor glass, an aggregate and a binder that constitutethe phosphor, a function of expanding the divergence angle of light as ascattering body for red light or infrared light could be given to thephosphor and that as a result, it was possible to prevent a phenomenonas an obstacle in imaging, such as a speckle generated by potentialinterference, when using the semiconductor laser.

(34) According to a ninth aspect of the invention, a light source deviceincludes a first light emitting device, a second light emitting deviceand a third light emitting device. The first light emitting device emitslight having a first wavelength. The second light emitting device emitslight having a second wavelength different from the first wavelength.The third light emitting device including or coated with one or morephosphors which are excited by the light emitted from the first lightemitting device to emit first fluorescent light having an emissionwavelength different from the first wavelength. An energy offluorescence light of the third light emitting device when the thirdlight emitting device is excited by light having the second wavelengthand having a certain energy is equal to or less than 1/10 of that offluorescence light of the third light emitting device when the thirdlight emitting device is excited by light having the first wavelengthand having the certain energy(35) In the light source device of (34), the energy of the fluorescencelight of the third light emitting device when the third light emittingdevice is excited by the light having the second wavelength and havingthe certain energy is equal to or less than 1/100 of that of thefluorescence light of the third light emitting device when the thirdlight emitting device is excited by the light having the firstwavelength and having the certain energy.(36) In the light source device of any one of (34) to (35), the energyof the fluorescence light of the third light emitting device when thethird light emitting device is excited by the light having the secondwavelength and having the certain energy is equal to or less than1/10,000 of that of the fluorescence light of the third light emittingdevice when the third light emitting device is excited by the lighthaving the first wavelength and having the certain energy.(37) In the light source device of any one of (34) to (36), the secondfluorescent light, which is emitted by excitation by the light emittedfrom the second light emitting device, can be substantially neglected ascompared with the first fluorescent light emitted by excitation by thelight emitted from the first light emitting device.(38) The light source device of any one of (34) to (37) may furtherinclude a first optical fiber that guides first excitation light emittedfrom the first light emitting device. The one or more phosphors of thethird light emitting device may be disposed at an emission end of thefirst optical fiber. The first fluorescent light emitted from the one ormore phosphors excited by the first excitation light guided by the firstoptical fiber may be mixed in the one or more phosphors of the thirdlight emitting device and be then emitted from the third light emittingdevice. Emission light of the second light emitting device may beemitted from the third light emitting device through the one or morephosphors of the third light emitting device.(39) The light source device of (38) may further include a secondoptical fiber that guides the emission light of the second lightemitting device. The one or more phosphors of the third light emittingdevice may be disposed to be positioned at an emission end of the secondoptical fiber. The emission light of the second light emitting devicemay be guided by the second optical fiber and be then emitted from thethird light emitting device through the one or more phosphors of thethird light emitting device.

Furthermore, a first optical fiber that guides first excitation lightemitted from the first light emitting device and a second optical fiberthat guides emission light of the second light emitting device may befurther provided. The phosphors of the third light emitting device maybe disposed at emission ends of the first and second optical fibers. Thefirst excitation light and the first fluorescent light emitted from thephosphors excited by the first excitation light guided by the firstoptical fiber may be mixed in the phosphors of the third light emittingdevice and be then emitted from the phosphors. The emission light of thesecond light emitting device may be guided by the second optical fiberand be then emitted from the phosphor through the phosphors of the thirdlight emitting device.

(40) In the light source device of (39), the first and second opticalfibers may be the same one optical fiber. The one optical fiber mayguide the first excitation light emitted from the first light sourcedevice and the emission light of the second light source device. The oneor more phosphors of the third light emitting device may be disposed atthe emission end of the one optical fiber. The first fluorescent lightemitted from the one or more phosphors excited by the first excitationlight guided by the one optical fiber may be mixed in the one or morephosphors of the third light emitting device and be then emitted fromthe third light emitting device. The emission light of the second lightemitting device may be guided by the one optical fiber and be thenemitted from the third light emitting device through the one or morephosphors of the third light emitting device.(41) In the light source device of any one of (38) to (39), the secondoptical fiber or the one optical fiber may include a germanium oxide ina core thereof.

Furthermore, one optical fiber that guides first excitation lightemitted from the first light emitting device and emission light of thesecond light emitting device may be provided. The phosphors of the thirdlight emitting device may be disposed at an emission end of the oneoptical fiber. The first excitation light and the first fluorescentlight emitted from the phosphors excited by the first excitation lightguided by the one optical fiber may be mixed in the phosphors of thethird light emitting device and be then emitted from the phosphors. Theemission light of the second light emitting device may be guided by theone optical fiber and be then emitted from the phosphor through thephosphors of the third light emitting device.

(42) In the light source device of (38), the second light emittingdevice may be mounted below the one or more phosphors of the third lightemitting device.(43) In the light source device of (34) to (37), the first and secondlight emitting devices may be mounted below the one or more phosphors ofthe third light emitting device.(44) In the light source device of (34) to (43), the second wavelengthof the emission light of the second light emitting device may include awavelength in an infrared region.(45) According to tenth aspect of the invention, an endoscope apparatusincludes the light source device of any one of (34) to (44).

According to the above-described configuration of any one of (34) to(45), it is possible to provide a light source device that can be madesmall and thin by making two emitted light components having differentwavelengths guided coaxially and that can be made at low cost and hasmany applications, and an endoscope apparatus using the light sourcedevice. Furthermore, according to the above-described configuration ofany one of (34) to (45), efficient white illumination andminiaturization of the device can be realized, and it is possible tomake emission sources of white light and infrared light almost the sameor the white light and the infrared light can be guided coaxially sothat the emission positions thereof can be made almost the same. Forexample, comparison between both images can be easily performed bydecreasing a difference between the images or appearance of shadows evenwhen the normal image under the white light and the image under theinfrared light are acquired in a time-series manner and displayed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating the conceptual configuration of anendoscope apparatus according to a first embodiment of the invention.

FIG. 2 is a view illustrating the configuration of an optical system ofa light source device for use in the endoscope apparatus shown in FIG.1.

FIG. 3 is a graph illustrating the spectrum distribution of light afterlaser beams mixed and emitted from light source sections arewavelength-converted by first and second wavelength conversion members.

FIG. 4 is an emission spectrum when a second wavelength conversionmember is excited by an infrared laser beam having a center wavelengthof 950 nm.

FIG. 5 is a configuration view of an optical system of a light sourcedevice, according to a second embodiment, for use in the endoscopeapparatus shown in FIG. 1.

FIG. 6 is a section view of an optical fiber shown in FIG. 5.

FIG. 7 is a view illustrating the conceptual configuration of anendoscope apparatus according to a third embodiment.

FIG. 8 is a view illustrating the configuration of an optical system ofa light source device for use in the endoscope apparatus shown in FIG.7.

FIG. 9 is a graph illustrating the spectrum distribution of light aftera blue laser beam is wavelength-converted by the first wavelengthconversion member.

FIG. 10 is a graph illustrating excitation spectrum and emissionspectrum of LiTbW₂O₈ used as the second wavelength conversion member.

FIG. 11 is a graph illustrating excitation spectrum and emissionspectrum of β-SiALON used as the second wavelength conversion member.

FIG. 12A is an explanatory view conceptually illustrating plural frameimages which are obtained in a time-series manner by imaging by animaging optical system.

FIG. 12B is an explanatory view conceptually illustrating a state wherethe frame images of FIG. 12A are rearranged and displayed.

FIG. 13 is an explanatory view schematically illustrating a state whereimaged signals stored in first and second memories are displayed indifferent display regions on a monitor, respectively.

FIG. 14 is an explanatory view illustrating main light components, whichare included in a screen of a specific detection color, for each frameimage.

FIG. 15 is a graph illustrating excitation spectrum and emissionspectrum of a CaAlSiN₃ red phosphor.

FIG. 16 is a view illustrating the conceptual configuration of theendoscope apparatus according to a fourth embodiment of the invention.

FIG. 17 is a view illustrating the schematic sectional configuration ofan illumination optical system at the tip of an endoscope insertionportion of the endoscope apparatus shown in FIG. 16.

FIG. 18 is emission spectrums of a blue LED device and a green emissionLED device of a specific color light illumination system.

FIG. 19A is an explanatory view conceptually illustrating plural frameimages which are obtained in a time-series manner by imaging by animaging optical system.

FIG. 19B is an explanatory view conceptually illustrating a state wherethe frame images of FIG. 19A are rearranged and displayed.

FIG. 20 is an explanatory view illustrating main light components, whichare included in a screen of a specific detection color, for each frameimage which is imaged in a similar manner to FIG. 19A.

FIG. 21 is an explanatory view illustrating a relationship between anobservation region and a specific color light irradiation region.

FIG. 22 is another section view illustrating the configuration of theendoscope insertion portion.

FIG. 23 is a view illustrating the configuration of another opticalsystem of the light source device.

FIG. 24 is emission spectrums of a blue LED device, a green emission LEDdevice, and an infrared emission LED device.

FIG. 25 is a schematic sectional view illustrating the endoscopeapparatus according to a fifth embodiment of the invention that uses alight source device.

FIG. 26 is a schematic view illustrating details of the light sourcedevice for use in the endoscope apparatus shown in FIG. 25.

FIG. 27 is a schematic sectional view illustrating an optical fiber usedin the light source device shown in FIG. 26.

FIG. 28 is a schematic sectional view illustrating the endoscopeapparatus according to a sixth embodiment of the invention that uses thelight source device.

FIG. 29 is a schematic sectional view illustrating details of the lightsource device for use in the endoscope apparatus shown in FIG. 28.

FIG. 30 is a schematic sectional view illustrating a blue LED deviceused in the light source device shown in FIG. 29.

FIG. 31 is a schematic sectional view illustrating an infrared emissionLED device used in the light source device shown in FIG. 29.

FIG. 32 is a schematic sectional view illustrating an endoscopeapparatus of a related art.

FIG. 33 is a schematic sectional view illustrating details of a lightsource device of the related art used in the endoscope apparatus shownin FIG. 32.

FIG. 34 is a schematic sectional view illustrating another example of alight source device of the related art in detail.

FIG. 35A schematically shows an emission spectrum of fluoroaluminumsilicate glass doped with Yb and Er when it is excited by light having425 nm in wavelength.

FIG. 35B schematically shows an emission spectrum of fluoroaluminumsilicate glass doped with Yb and Er when it is excited by light having850 nm in wavelength.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION First Embodiment

Hereinafter, a light source device according to a first embodiment andan endoscope apparatus using the light source device will be describedin detail with reference to the accompanying drawings. FIG. 1 is a viewillustrating the conceptual configuration of the endoscope apparatusaccording to the first embodiment. An endoscope apparatus 100 of thefirst embodiment is configured to mainly include an endoscope 10, alight source device 20, an image processing device 30, and a monitor 40.The endoscope 10 includes a main body operation portion 11 and aninsertion portion 13 which is provided to be connected to the main bodyoperation portion 11 and is inserted into a body to be inspected (bodycavity). A solid-state imaging device 15 and an imaging lens 17 whichconstitute an imaging optical system are disposed in a tip portion ofthe insertion portion 13. Moreover, an illumination optical member 19,which is an illumination optical system, and an optical fiber 21connected to the illumination optical member 19 are disposed near theimaging optical system. Also, the optical fiber 21 is connected to thelight source device 20, which will be described in detail later. Animaging signal from the solid-state imaging device 15 is input to theimage processing device 30.

An imaging device, such as a CCD (charge coupled device) or a CMOS(complementary metal-oxide semiconductor), is used as the solid-stateimaging device 15. The imaging signal is converted into image data by animaging signal processing section 27 based on a command from a controlsection 29, and appropriate image processing is performed for the imagedata. The control section 29 outputs the image data output from theimaging signal processing section 27, as an image, to the monitor 40.The optical fiber 21 guides light emitted from a light source section31, which will be described later, of the light source device 20 to thetip of the insertion portion 13. The light source device 20 isconfigured to include the light source section 31, the optical fiber 21,and the illumination optical member 19.

Next, an example of the configuration of the light source section 31will be described. FIG. 2 is a view illustrating the configuration of anoptical system of the light source device used in the endoscopeapparatus shown in FIG. 1. The light source device 20 has: a blue laserlight source 33 (an example of a first light source) having a centerwavelength of 445 nm; an infrared laser light source 35 (an example ofsecond light source) having a center wavelength of 980 nm; collimatorlenses 37, 37 which collimate laser beams from the blue laser lightsource 33 and the infrared laser light source 35; a polarization beamsplitter 39 which is an optical coupling unit that polarize and couplestwo laser beams; a condensing lens 41 which condenses laser beamscoupled on the same optical axis by the polarization beam splitter 39;and the optical fiber 21.

The blue laser light source 33 is a broad area type InGaN laser diode.Moreover, an InGaNAs laser diode or a GaNAs laser diode may also beused.

The infrared laser light source 35 is a broad area type InGaAssemiconductor laser which emits an infrared ray that is invisible light.

A laser beam from the blue laser light source 33 and a laser beam fromthe infrared laser light source 35 are coupled by the polarization beamsplitter 39 and are then input to the optical fiber 21 by the condensinglens 41. The optical fiber 21 allows the input laser beam to propagateup to the tip of the insertion portion 13 (refer to FIG. 1) of theendoscope 10.

On the other hand, on the light emission side of the optical fiber 21, acondensing lens 43 which constitutes the illumination optical member 19is disposed, and a first wavelength conversion member 45 and a secondwavelength conversion member 47 which are integrated are also disposed.Moreover, although not shown, on the tip surface of the insertionportion 13 of the endoscope 10, the illumination optical member 19 isdisposed with a cover glass or a lens interposed therebetween. The firstwavelength conversion member 45 has a phosphor including plural types ofphosphors which absorb and are excited by a part of the laser beam fromthe blue laser light source 33 so as to emit light of green to yellow.Then, the laser beam from the blue laser light source 33 and theexcitation light of green to yellow converted from the laser beams aremixed to generate white light.

The second wavelength conversion member 47 is made of an up-conversionmaterial which absorbs and is excited by the laser beam from theinfrared laser light source 35 so as to emit green light. An example ofthe up-conversion material includes oxide-fluoride-based crystallizedglass. For example, high-efficiency infrared/visible conversiontransparent glass ceramic or transparent body crystal described in JPHei.7-69673 A (corresponding to U.S. Pat. Nos. 5,420,080 and 5,545,595)and JP Hei.7-97572 A (corresponding to U.S. Pat. No. 5,439,616) may beused as the second wavelength conversion member 47. Moreover, arare-earth element may also be added to the oxide-fluoride-basedcrystallized glass as a base material. It is assumed that an addedrare-earth element is erbium (Er), for example. In this case, when it isexcited by infrared light of a broad band semiconductor laser having awavelength of 808 nm, emitted color light can be freely controlled, forexample, according to the concentration of Er. For example, at 0.1 to 1mol %, green light is emitted. As the concentration increases, light isemitted gradually on the long wavelength side. Yellow light can beemitted when the concentration of Er exceeds 2.0 mol %, and red lightcan be emitted at 5.0 mol %. In addition to those described above, theemission efficiency of green light may also be increased by adding Erand an yttrium (Y) to the oxide-fluoride-based crystallized glass.Alternatively, only Er may be added.

The second wavelength conversion member 47 is made of, for example, aYb³⁺—Er³⁺-based up-conversion phosphor, and the basic composition isSiO₂(GeO₂)—PbF₂—ReF₃(Re:Yb, Er) of three component system. As anexample, ‘YAGLASS (product name)’ of Sumita Optical Glass, Inc. isavailable. The composition is22SiO₂-10GeO₂-15AlO_(1.5)-3TiO₂-39PbF₂-10YbF₃-1ErF₃ in mol %.

With the above-described configuration, each laser beam emitted from theoptical fiber 21 is irradiated to the first wavelength conversion member45, and the first wavelength conversion member 45 absorbs a part of bluelaser beam from the blue laser light source 33, performs wavelengthconversion of the absorbed blue laser beams, and is excited to emitlight (light of green to yellow) which has a longer wavelength than theblue laser beam. In addition, the other part of the blue laser beam andthe infrared laser beam of the infrared laser light source 35 aretransmitted through the first wavelength conversion member 45 withoutbeing absorbed by the first wavelength conversion member 45, and arethen incident on the second wavelength conversion member 47 togetherwith the excitation light of the first wavelength conversion member 45.The second wavelength conversion member 47 absorbs a part of or all ofthe infrared laser beams and is excited to emit narrowband green light.As a result, white light obtained by mixing of (i) the blue laser beams,(ii) the green to yellow light emitted by excitation of the firstwavelength conversion member 45 and (iii) the narrowband green lightemitted by excitation of the second wavelength conversion member 47 areemitted frontward on the optical path. In addition, the first wavelengthconversion member 45 and the second wavelength conversion member 47 maybe disposed separately without being integrated. Moreover, one block inwhich materials having respective functions are finely mixed andarranged may be advantageous in reducing the space.

Furthermore, as compared with the case where a laser beam is emitted asillumination as it is, since the green light obtained by excitation bythe infrared light is irradiated, it hardly occurs that a noise issuperimposed on a captured image or flickering occurs on a moving imagedue to speckle (interference) by a laser beam. In addition, if aselective reflection film for the infrared light for suppressingemission of unnecessary infrared light is provided on a converted lightemission side of the second wavelength conversion member 47 located atthe tip, the infrared light is incident again on the second wavelengthconversion member 47. Thereby, emission of green light can be moreintensified.

Moreover, if the second wavelength conversion member 47 located at thetip is divided into two semicircular parts and if the Er density in oneof the parts is set to 0.5% and the Er density in the other part is setto 5%, narrow-band green light and red light can be emittedsimultaneously by infrared light. In this case, narrowband green lightand red light can be emitted simultaneously. Alternatively, such lightcomponents may be emitted separately.

FIG. 3 is a graph illustrating the spectrum distribution of light afterthe laser beams coupled and emitted from the light source section 31 iswavelength-converted by the first wavelength conversion member 45 andthe second wavelength conversion member 47. The laser beam from the bluelaser light source 33 is represented by an emission line having a centerwavelength of 445 nm Light emitted from the first wavelength conversionmember 45 excited by the laser beam increases the intensity of theemission light in a wavelength band of approximately 450 nm to 700 nm.White light is formed by light within this wavelength band and a bluelaser beam. In addition, light emitted from the second wavelengthconversion member 47 excited by the infrared laser beam from theinfrared laser light source 35 superimposes the intensity of theemission light in a narrow wavelength band of about 530 to 570 nm.

FIG. 4 is an emission spectrum when the second wavelength conversionmember 47 is excited by an infrared laser beam having a centerwavelength of 950 nm. Light emitted in a wavelength band of 550 nm isgreen light emitted by Er³⁺, and light emitted in a wavelength band of660 nm is red light emitted by Er³⁺. That is, the green emitted lightincreases the emission intensity near 550 nm in FIG. 3. In addition,although the red light generated from the second wavelength conversionmember 47 is emitted together with green light, a green light componentand a red light component can be easily separated by using a colorfilter provided in the solid-state imaging device 15, for example, bydetecting only a green light component with the solid-state imagingdevice 15. Accordingly, a problem of color mixture does not occur insubsequent signal processing.

Next, a use example of the endoscope apparatus 100 when the light sourcedevice 20 having the above-described configuration is built into theendoscope 10 will be described. As shown in FIG. 1, in the endoscopeapparatus 100, the insertion portion 13 of the endoscope 10 is insertedinto the body cavity, illumination light is irradiated through theillumination optical member 19 from the tip of the insertion portion 13,and the reflected light is imaged through the imaging lens 17 in thesolid-state imaging device 15. An imaging signal obtained by the imagingis output to the monitor 40 after being subjected to the appropriateimage processing by the imaging signal processing section 27. Or, theimaging signal is stored in a recording medium.

In case of imaging using such a solid-state imaging device 15, at thetime of normal endoscopic diagnosis in which observation is made byirradiating white illumination light within the body cavity, the controlsection 29 turns on an output of a laser beam from the blue laser lightsource 33 and turns off the infrared laser light source 35 or blocks theoutput of the infrared laser light source 35 with a shutter. In thiscase, irradiated is white illumination light, which is generated by thelaser beam from the blue laser light source 33 and the light emitted byexcitation of the first wavelength conversion member 45. Moreover, whenperforming spectral diagnostics with the endoscope apparatus 100, thecontrol section 29 turns on outputs of the blue laser light source 33and the infrared laser light source 35 simultaneously so thatillumination light having the emission spectrum shown in FIG. 3 isirradiated. Furthermore, the light irradiation may also be performedwhile making a proper adjustment of turning on only the infrared laserlight source 35 or turning on the outputs of the blue laser light source33 and the infrared laser light source 35 simultaneously in a statewhere the output of the blue laser light source 33 is reduced.

Also, laser beams from the infrared laser light source 35, whichgenerates light in a specific narrow visible wavelength band, areinvisible light. Therefore, the color balance of illumination lightemitted is not affected even if a part of the laser beams aretransmitted through the second wavelength conversion member 47 withoutall of the laser beams from the infrared laser light source 35 beingwavelength-converted by the second wavelength conversion member 47.Accordingly, the diagnostic precision of the endoscope can be maintainedhigh without causing a color change in an observed image within the bodycavity. In addition, the infrared laser beams from the infrared laserlight source 35 are hardly absorbed by the first wavelength conversionmember 45. Accordingly, since a drop in light intensity is small, anillumination optical system with high light use efficiency can be built.

Second Embodiment

Next, a second embodiment in which the second wavelength conversionmember 47 of the light source device 20 is provided within an opticalfiber will be described. FIG. 5 is a configuration view of an opticalsystem illustrating another example of a light source device used in theendoscope apparatus of FIG. 1. Here, description on members which arethe same as those in FIG. 2 will be omitted or simplified with the samereference numerals being assigned thereto. The configuration of a lightsource device 50 is the same as the above-described configuration exceptthat a material of the second wavelength conversion member 47 iscontained in a light guiding material of the entire optical fiber 53 ora part of the optical fiber 53 instead of providing a block of thesecond wavelength conversion member 47 on the light emission side of theoptical fiber 53.

FIG. 6 shows a section view of the optical fiber 53 shown in FIG. 5. Theoptical fiber 53 is configured to include a core 55 having a circularcross section, a first cladding 57 which is disposed outside the core 55and has an approximately rectangular section, and a second cladding 59which is disposed outside the first cladding 57 and has a circularsection. The core 55 is made of a Zr-based fluoride glass doped withPr³⁺, for example, ZBLANP (ZrF₄—BaF₂-LaF₃—AlF₃—AlF₃—NaF—PbF₂). The firstcladding 57 is made of ZBLAN (ZrF₄—BaF₂—LaF₃—AlF₃—NaF) as an example,and the second cladding 59 is made of a polymer as an example.

In addition, the core 55 may be formed using not only the ZBLANP butalso ZBLAN or In/Ga-based fluoride glass, for example, IGPZCL, that is,(InF₃—GaF₃—LaF₃)-(PbF₂—ZnF₂)—CdF.

With the above-described configuration, a laser beam having a wavelengthof 445 nm and a laser beam having a wavelength of 950 nm, which arecondensed by the condensing lens 41, are input to the first cladding 57of the optical fiber 53 and propagate therethrough in a waveguide mode.That is, the first cladding 57 acts as a core for a laser beam which isexcitation light.

A laser beam also passes through a portion of the core 55 whilepropagating as described above. In the core 55, Pr³⁺ is excited by theincident laser beam, thereby generating fluorescent light having awavelength of 491 nm. The fluorescent light propagates through the core55 in the waveguide mode and is emitted from an emission end 53 b of theoptical fiber 53 forward on the optical path.

In addition, the fluorescent light may also be laser-oscillated andemitted. For example, in the core 55 made of ZBLANP, fluorescent lighthaving a wavelength of 520 nm by transition of 3P1->3H5, fluorescentlight having a wavelength of 605 nm by transition of 3P0->3F2, andfluorescent light having a wavelength of 635 nm by transition of3P0->3F3 may be generated in addition to the above fluorescent light.Therefore, an incidence end 53 a of the optical fiber 53 is coated suchthat HR (high reflection) is realized for the wavelength of 491 nm andAR (antireflection) is realized for the wavelengths of 520 nm, 605 nm,and 635 nm and a wavelength of 950 nm causing excitation light, and theemission end 53 b of the optical fiber 53 is coated to allow only 1% oflight having the wavelength of 491 nm to be transmitted therethrough.

With such coating, the fluorescent light having the wavelength of 491 nmresonates between both the ends 53 a and 53 b of the optical fiber 53 tocause laser oscillation. Then, a blue-green laser beam having awavelength of 491 nm obtained as described above can be emitted from theemission end 53 b of the optical fiber 53 frontward on the optical path.

Moreover in this example, a laser beam having a wavelength of 445 nmpropagates through the core 55 in a single mode, while a laser beamhaving a wavelength of 950 nm which is excitation light propagatesthrough the first cladding 57 in a multimode. This makes it possiblethat a laser beam from the infrared laser light source 35 is input tothe optical fiber 53 with high coupling efficiency.

In addition, since the sectional shape of the first cladding 57 isalmost rectangular, the laser beam from the infrared laser light source35 follows an irregular reflecting path within a cladding section.Accordingly, a probability of the laser beam being incident on the core55 is increased. As a result, since high oscillation efficiency issecured, a high-output green-blue laser beam can be obtained.

With the above-described configuration, the illumination optical member19 disposed at the tip of the insertion portion 13 of the endoscope 10requires only the first wavelength conversion member 45. As a result,the insertion portion 13 of the endoscope 10 can be made compact. Inaddition, a material of the second wavelength conversion member 47 maybe disposed at any position so long as its position is anterior to theincidence side 53 a of the optical fiber 53 on the optical path.

Third Embodiment

Hereinafter, a light source device according to a third embodiment, anendoscope apparatus using this light source device, and an imageprocessing method will be described in detail with reference to theaccompanying drawings. FIG. 7 is a view illustrating the conceptualconfiguration of the endoscope apparatus according to the thirdembodiment. An endoscope apparatus 101 is configured to mainly includean endoscope 110, a light source device 120, an image processing device130, and a monitor 140. The endoscope 110 includes a main body operationportion 111 and an insertion portion 113 which is provided to beconnected to the main body operation portion 111 and is inserted into abody to be inspected (body cavity). A solid-state imaging device 115 andan imaging lens 117 which constitute an imaging optical system aredisposed in a tip portion of the insertion portion 113. Moreover, anillumination optical member 119, which constitutes an illuminationoptical system, and an optical fiber 121 connected to the illuminationoptical member 119 are disposed near the imaging optical system. Theoptical fiber 121 is connected to the light source device 120, whichwill be described in detail later. An imaging signal from thesolid-state imaging device 115 is input to the image processing device130.

An imaging device, such as a CCD or a CMOS, is used as the solid-stateimaging device 115. The imaging signal is converted into image data byan imaging signal processing section 127 based on a command from acontrol section 129 and appropriate image processing is performed forthe image data. The control section 129 outputs the image data outputfrom the imaging signal processing section 127, as an image, to themonitor 140 which is an example of an imaged image display unit.Moreover, a first memory 151 and a second memory 152 for storing imagingsignals are connected to the control section 129. The first and secondmemories 151 and 152 will be described later. The optical fiber 121guides light emitted from a light source section 131, which will bedescribed later, of the light source device 120 to the tip of theinsertion portion 113. The light source device 120 is configured toinclude the light source section 131, the optical fiber 121, and theillumination optical member 119.

Next, an example of the configuration of the light source section 131will be described. FIG. 8 is a view illustrating the configuration of anoptical system of the light source device used in the endoscopeapparatus shown in FIG. 7. The light source device 120 has: a blue laserlight source 133 (an example of a first light source) having a centerwavelength of 445 nm; a near-ultraviolet laser light source 135 (anexample of a second light source) having a center wavelength of 375 nm;collimator lenses 137, 137 which collimate laser beams from the bluelaser light source 133 and the near-ultraviolet laser light source 135;a polarization beam splitter 139 which is an optical coupling unit thatpolarizes and couples two laser beams; a condensing lens 141 whichcondenses laser beams coupled on the same optical axis by thepolarization beam splitter 139; and the optical fiber 121. In addition,the control section 129 functions as a control unit that controlsemission of laser beams from the blue laser light source 133 and thenear-ultraviolet laser light source 135.

The blue laser light source 133 is a broad area type InGaN laser diode.

The near-ultraviolet laser light source 135 is a broad area type InGaNsemiconductor laser which emits a near-ultraviolet ray that is invisiblelight. In addition, although a laser which emits a near-ultraviolet rayis described herein, a purple laser having a center wavelength of 405 nmmay be used, or a light source which emits purple to near-ultravioletlaser light may be used.

The laser beam from the blue laser light source 133 and the laser beamfrom the near-ultraviolet laser light source 135 are coupled by thepolarization beam splitter 139 and are then input to the optical fiber121 by the condensing lens 141. The optical fiber 121 allows the inputlaser beam to propagate up to the tip of the insertion portion 113 ofthe endoscope 110 (see FIG. 7).

On the other hand, on the light emission side of the optical fiber 121,a condensing lens 143 which constitutes the illumination optical member119 is disposed, and a wavelength conversion member 145 in which firstand second wavelength conversion members are integrated is disposed. Thewavelength conversion member 145 is an integrated block in which pluraltypes of phosphors are distributed. Moreover, although not shown, on thetip surface of the insertion portion 113 of the endoscope 110, theillumination optical member 119 is disposed with a cover glass or a lensinterposed therebetween. The first wavelength conversion member whichconstitutes the wavelength conversion member 145 is configured toinclude plural types of phosphors (for example, a YAG-based phosphor ora phosphor including BAM (BaMgAl₁₀O₃₇)) which absorb a part of the laserbeam from the blue laser light source 133 and are excited to emit lightof green to yellow. Then, the laser beam from the blue laser lightsource 133 and the excitation light of green to yellow converted fromthe laser beam are mixed to generate white light.

The second wavelength conversion member which also constitutes thewavelength conversion member 145 is made of a down-conversion materialwhich absorbs the laser beam from the near-ultraviolet laser lightsource 135 and is excited to emit light of green. As the down-conversionmaterial, for example, LiTbW₂O₈ which is a green phosphor (see TsutomuOdaki, “Phosphor for White LED”, IEICE Technical Research ReportED2005-20, CFM2005-28, SDM2005-28, pp. 69-74 (2005-05), and the like),beta SiALON (β-SiALON: Eu) blue phosphor (see Naoto Hirosaki, Xie RongJun and Ken Sakuma, “New SiALON phosphors and white LEDs”, Transactionsof JSAP, Vol. 74, No. 11, pp. 1449-1452 (2005), or Hajime Yamamoto,School of Bionics, Tokyo University of Technology, Transactions of JSAP,Vol. 76, No. 3, p. 241 (2007)) may be used. β-SiALON is crystalexpressed as composition of Si_(b)-zAl₂O₂N₈-z (z is solid solubleamount) in which aluminum and acid are solid-dissolved in β-type siliconnitride crystal. Here, both LiTbW₂O₈ and β-SiALON are mixed as thesecond wavelength conversion member. In addition, the configuration inwhich both phosphors may be stacked in the layer shape may also beadopted. In the wavelength conversion member 145, the phosphors includedin the first and second wavelength conversion members are randomlydistributed to be formed as an integrated body. In addition to randomlydistributing the phosphors, a proper modification may be made accordingto a phosphor material, for example, by forming the first and secondwavelength conversion members as fine blocks and then bonding the fineblocks to each other or adopting a laminated structure in which the fineblocks are stacked in the layer shape.

With the above-described configuration, each laser beam emitted from theoptical fiber 121 is irradiated to the wavelength conversion member 145,and the wavelength conversion member 145 absorbs a part of the bluelaser beam from the blue laser light source 133 by the first wavelengthconversion member and is excited to emit light (light of green toyellow) which has a longer wavelength than the blue laser beam. Inaddition, the wavelength conversion member 145 absorbs a part of or allof the near-ultraviolet laser beam from the near-ultraviolet laser lightsource 135 and is excited to emit narrowband green light and blue light.As a result, white light obtained by mixing of the blue laser beam, thegreen to yellow light emitted by excitation of the first wavelengthconversion member and the narrowband green light and blue light emittedby excitation of the second wavelength conversion member is emittedforward on the optical path. Each of the wavelength conversion membersis selected so that a blue laser beam is transmitted through the secondwavelength conversion member without being absorbed by the secondwavelength conversion member and that a near-ultraviolet laser beam istransmitted through the first wavelength conversion member without beingabsorbed by the first wavelength conversion member.

As compared with the case where a laser beam is emitted as illuminationas it is, since the green and blue light obtained by excitation by thenear ultraviolet light is irradiated, it hardly occurs that a noise issuperimposed on a captured image or flickering occurs on a moving imagedue to speckle (interference) by a laser beam. In addition, if aselective reflection film for near-ultraviolet light for suppressingemission of unnecessary near-ultraviolet light is provided on aconverted light emission side of the wavelength conversion member 145,the near-ultraviolet light is incident again on the wavelengthconversion member 145. Accordingly, in this case, emission of greenlight and narrowband blue light can be more intensified. Moreover, incase of using a purple laser instead of near-ultraviolet light, it ispreferable to provide a selective reflection film of purple lightsimilarly.

FIG. 9 is a graph illustrating the spectrum distribution of light afterthe blue laser beam is wavelength-converted by the first wavelengthconversion member. The blue laser beam from the blue laser light source133 is represented by an emission line having a center wavelength of 445nm. Light emitted from the first wavelength conversion member excited bythe laser beam increases the emission intensity in a wavelength band ofapproximately 450 nm to 700 nm White light is formed by the light withinthis wavelength band and the blue laser beam.

FIG. 10 is an excitation spectrum and an emission spectrum of LiTbW₂O₈used as the second wavelength conversion member. In the case ofLiTbW₂O₈, a sharp excitation band exists near a wavelength of 375 nm, sothat a near-ultraviolet laser beam having a center wavelength of 375 nmcan be efficiently wavelength-converted. In addition, light which has awavelength of 544 nm as a center wavelength and which is emitted bytransition of 5D4->7F5 of Tb³⁺ ion becomes high-intensity light having anarrow wavelength band, that is, having about 20 nm in full width athalf maximum.

FIG. 11 is an excitation spectrum and an emission spectrum of β-SiALONsimilarly used as the second wavelength conversion member. The β-SiALONis a phosphor which absorbs light having a wavelength of 350 to 430 nmto emit light corresponding to blue to blue-green of 450 to 520 nm. Theβ-SiALON can realize wavelength conversion of a near-ultraviolet laserbeam having a center wavelength of 375 nm efficiently. Accordingly, thelight source device 120 can selectively emit the white light shown inFIG. 8, the green light having the center wavelength of 544 nm shown inFIG. 10, or the blue to blue-green light having the wavelength of 450 to520 nm shown in FIG. 11. In addition, although green light, blue light,and emitted light in other wavelength bands generated from the secondwavelength conversion member are emitted simultaneously, a green lightcomponent and other light components can be easily separated by using acolor filter provided in the solid-state imaging device 115, forexample, by detecting only a green light component with the solid-stateimaging device 115. Moreover, a blue light component may be separatedsimilarly. Accordingly, a problem of color mixture does not occur insubsequent signal processing.

Next, a use example of the endoscope apparatus 101 when the light sourcedevice 120 having the above-described configuration is built into theendoscope 110 will be described. As shown in FIG. 7, in the endoscopeapparatus 101, the insertion portion 113 of the endoscope 110 isinserted into the body cavity, and illumination light is irradiatedthrough the illumination optical member 119 from the tip of theinsertion portion 113. The reflected light is imaged through the imaginglens 117 in the solid-state imaging device 115. An imaging signalobtained by the imaging is output to the monitor 140 after beingsubjected to the appropriate image processing by the imaging signalprocessing section 127. Or, the imaging signal is stored in a recordingmedium.

In case of imaging using this solid-state imaging device 115, at thetime of normal endoscopic diagnosis in which observation is made byirradiating white illumination light within the body cavity, the controlsection 29 turns on an output of a laser beam from the blue laser lightsource 133 shown in FIG. 8 and turns off the near-ultraviolet laserlight source 135 or blocks the output with a shutter. In this case, thewhite illumination light generated by the laser beam from the blue laserlight source 133 and the light emitted by excitation of the firstwavelength conversion member of the wavelength conversion member 145 isirradiated to the body to be inspected. Moreover, when spectraldiagnostics is performed with the endoscope apparatus 101, the controlsection 29 turns on the output of the near-ultraviolet laser lightsource 135 so as to irradiate green light and blue light to a body to beinspected. Then, reflected light from the body to be inspected to whichnarrowband green light and blue light are irradiated simultaneously isimaged to generate a pseudo color image for spectral diagnostics. Forexample, the pseudo color image is generated by converting a greendetection signal (reflected light component of narrowband green light)obtained by the imaging device 115 into a red color tone and convertinga blue detection signal into blue and green color tones. With thispseudo color image, a surface microstructure (for example, amicrostructure of a capillary vessel or a mucous membrane) of a surfacelayer of a body to be inspected can be clearly observed. For example,drawing of pit and surface blood vessel can be observed with the bluelaser beam having the center wavelength of 445 nm, and flare or a fineblood vessel in a deep place can be observed with the narrowband greenlight by β-SiALON, having the center wavelength of 532 nm.

Here, a specific control example of spectral diagnostics will bedescribed. FIG. 12A is a view illustrating plural frame images obtainedin a time-series manner by imaging with the imaging optical system, andFIG. 12B is an explanatory view conceptually illustrating a state wherethese frame images are rearranged and displayed. Here, an observed imageunder illumination light of white light and an observed image underillumination light in a specific visible wavelength band (green, blue)are separately displayed on the monitor 140. As shown in FIG. 12A, thecontrol section 129 controls the light source section 131 to emit theblue laser beam having the center wavelength of 445 nm in a first frame,thereby irradiating the white light to the body to be inspected. Theimaging device 115 images the body to be inspected illuminated by thewhite light and stores the imaging signal in the first memory 151.

Then, the control section 129 controls the light source section 131 toemit the near-ultraviolet laser beam having the center wavelength of 375nm in a second frame, thereby irradiating the green light and the bluelight generated by the second wavelength conversion member to the bodyto be inspected. The imaging device 115 images the body to be inspectedilluminated by the green light and the blue light and stores the imagingsignal in the second memory 153.

Hereinafter, in the same manner as described above, processing ofirradiation (illumination) of light, imaging, and storing of an imagingsignal is repeatedly performed similarly to the first frame in a thirdframe (odd frame) and similarly to the second frame in a fourth frame(even frame). That is, the illumination of the white light and theillumination including light in the specific visible wavelength band arealternately switched every imaging frame of the imaging device 115.Then, as shown in FIG. 12B, the illumination images under the whitelight are accumulated in the first memory 151, and the images fornarrowband diagnosis under the green light and the blue light areaccumulated in the second memory 153. As image information based onthese two types of imaging signals, the imaging signals stored in thefirst and second memories are displayed in different display regions 155and 157 on the monitor, as shown in FIG. 13. Although the sizes of thedisplay regions are set equal in the example shown in FIG. 13, the sizesmay be set arbitrarily. For example, one of the display regions may bedisplayed larger than the other display region, or the other image maybe displayed small within one display region.

Thus, by alternately imaging an image under the illumination of thewhite light and an image under the illumination including the light inthe specific visible wavelength band, both the images can be acquiredapproximately at the same time. Accordingly, two types of imageinformation can be simultaneously displayed in real time. In addition,since the observation position and the property of the observed portioncan be understood simultaneously by displaying the imaged images side byside, the diagnostic precision based on the spectral diagnostics can befurther improved.

Moreover, when imaging is performed by irradiating the light in thespecific visible wavelength band, the combination of various lightcomponents is also available in addition to the combination of greenexcitation light of LiTbW₂O₈ and illumination light of blue excitationlight by β-SiALON as described above. For example, an observed imagewhen irradiating narrowband illumination light independently in a pseudomanner can be obtained with the laser beam from the blue laser lightsource 133. In this case, an image calculation process over frame imageswith different imaging timings is performed for plural frame imagesobtained in a time-series manner by imaging with the imaging opticalsystem. That is, a frame image configured to include plural screens ofdetection color screens (screens of three primary colors of blue, green,and red) obtained by detection of light components with differentspecific wavelength bands is imaged multiple times, while lightcomponents from plural types of light sources are irradiated insynchronization with the imaging timing of each frame image and indifferent conditions. Assuming that an observed image when a body to beinspected is illuminated by the first light source is referred to as afirst frame image and that an observed image when a body to be inspectedis illuminated by the second light source is referred to as a secondframe image, an observed image under light having a specific wavelengthcomponent from the light source is analytically obtained by repeatedlyimaging the first and second frame images and performing the calculationprocess for brightness information of a specific detection color screenof the first frame image and brightness information of a specificdetection color screen of the second frame image.

Main light components, which are included in a screen of a specificdetection color, for each frame image imaged in a similar manner toFIGS. 12A and 12B are shown in FIG. 14. Here, instead of a YAG phosphor,a β-SiALON green phosphor and a CaAlSiN₃ red phosphor are used as thefirst wavelength conversion member. Thus, a phosphor is used which isexcited to emit light even if light has any wavelength of 375 nm and 445nm. The excitation spectrum and emission spectrum of the CaAlSiN₃ redphosphor are shown in FIG. 15. The CaAlSiN₃ red phosphor is efficientlyexcited by blue light having a wavelength of 450 nm and emits red lightnear 650 nm. With this combination of the phosphors, the wavelengthconversion member 145 can be excited to emit light by light from any ofthe blue laser light source 133 (refer to FIG. 8) and thenear-ultraviolet laser light source 135. Thus, since the amount of lightcomponents emitted is increased, the light use efficiency is improved.

As shown in FIG. 14, in the first frame that is an imaging signalobtained by imaging under irradiation of the laser beam having thecenter wavelength of 445 nm, a blue detection light screen B1 includesan observation light based on illumination light of (i) the laser beamhaving the center wavelength of 445 nm from the blue laser light source133 and (ii) blue fluorescent light by β-SiALON of the first wavelengthconversion member, a green detection light screen G1 includes anobservation light based on illumination light of green fluorescent lightby β-SiALON of the first wavelength conversion member, and a reddetection light screen R1 includes an observation light based onillumination light of red fluorescent light by CaAlSiN₃ of the firstwavelength conversion member. Then, in the second frame that is animaging signal obtained by imaging under irradiation of the laser beamhaving the center wavelength of 375 nm, a blue detection light screen B2includes observation light based on illumination light of the bluefluorescent light by β-SiALON of the second wavelength conversionmember, a green detection light screen G2 includes observation lightbased on illumination light of (i) green fluorescent light by β-SiALONof the second wavelength conversion member and (ii) narrowband greenfluorescent light by LiTbW₂O₈ of the second wavelength conversionmember, and a red detection light screen R2 includes observation lightbased on illumination light of the red fluorescent light from CaAlSiN₃of the second wavelength conversion member.

Then, in the third frame that is an imaging signal obtained by imagingunder irradiation of the laser beam having the center wavelength of 445nm has the same light components as the first frame. Similarly, thefourth frame has the same light components as in the second frame, andthe fifth frame has the same light components as in the third frame(first frame), and these are repeated.

Here, although the observation light under the narrowband greenfluorescent light by LiTbW₂O₈ of the second wavelength conversion memberis included in G1 of the first frame, the observation light issuperimposed on the observation light based on the blue fluorescentlight by β-SiALON and becomes a broadband spectrum. Accordingly, theobservation light based on the original narrowband green fluorescentlight cannot be detected directly. For this reason, by subtracting thegreen detection light screen G1 of the first frame from the greendetection light screen G2 of the second frame in order to offset a greenfluorescent component of β-SiALON, observation light based on only thenarrowband green fluorescent component by LiTbW₂O₈ can be selectivelyextracted.

Similarly, although the laser beam having the wavelength of 445 nm inthe narrow wavelength band is also included in B1 of the first frame,the laser beam cannot be detected directly because the laser beam issuperimposed on blue fluorescent light based on β-SiALON. Therefore, bysubtracting B2 from B1, observation light based on only the laser beamhaving a wavelength of 445 nm can be extracted selectively.

Moreover, also for an observation light image obtained under whitelight, it becomes possible to acquire an image including a larger amountof information by performing the above-described process between frames.Although the observation light based on the white light illumination isobtained in the first and third frames (odd frames), it can improvecolor rendering properties by using the blue fluorescent light, whichhas a relatively wide wavelength bandwidth, based on β-SiALON in thesecond frame rather than by using the illumination light in which alaser beam as a bright line component is mixed. Thus, an observationlight image obtained under based on white light, which has better colorrendering properties, can be obtained by combining G1 and R1 of thefirst frame with B2 of the second frame without using the first frame asthe observation light image obtained under the white light.

In addition, the narrowband green fluorescent component based onLiTbW₂O₈ obtained by G2-G1 and the observation light image based on thelaser beam component having the wavelength of 445 nm obtained by B1-B2can be obtained as an observation light image based on narrowbandillumination light. Moreover, it is needless to say that arbitrarysetting can be made to such combinations. For example, an observed imageilluminated (white-illuminated) by the blue laser beam having the centerwavelength of 445 nm, an observed image illuminated by the green laserbeam having the center wavelength of 405 nm in the narrow wavelengthband of green, and an observed image illuminated by the emittedexcitation light in the wide wavelength band of blue based on thenear-ultraviolet laser beam having the center wavelength of 375 nm maybe acquired in the first, second, and third frames, respectively, andthey may be subjected to the calculation process in the respectiveframes.

As described above, image information convenient for diagnosis can beeasily provided by using the proper combination of the detection lightscreens of the frames obtained by the imaging. For example, observationlight based on the laser beam having the wavelength of 445 nm isacquired by an operation (B1-B2), and the acquired observation light isassigned to blue and green color tones. Observation light based onnarrowband green fluorescent light by LiTbW₂O₈ is acquired by anoperation (G2-G1), and the acquired observation light is assigned to ared color tone. Thus, by generating a emphasized image having a pseudocolor by converting an observed image based on light with a specificwavelength component into a specific color tone, a capillary vessel of atissue surface layer, a gland tube structure (pit pattern), and the likeare emphasized, which may greatly contribute to finding a malignanttumor at which capillary vessels concentrate.

By (i) a combination of phosphors suitable for acquisition of an imagingsignal in a narrow band of blue or green, (ii) switching of excitationlight sources in time-series manner, and (ii) a signal calculationmethod which is useful for the endoscope described above, an emissionwavelength band can be clearly separated by switching of excitationlight, and selective emission can be realized.

Accordingly, it is possible to easily acquire an image in which acapillary vessel of a surface layer of the tissue is clearly formed byblue light which is difficult to reach a deep portion of a mucousmembrane and in which a blood vessel of a deep portion is clearly formedby green light which arrives even at the inside of the tissue. Moreover,in the above description, the illumination light is obtained by turningon one of the blue laser light source 133 and the near-ultraviolet laserlight source 135 and turning off the other. In addition to this method,however, a light component in a desired emission wavelength band mayalso be extracted by turning on both the laser light sources to excite aphosphor and performing proper calculation processing for an imagedimage obtained by imaging in this state.

As described above, according to the endoscope apparatus 101, since thelaser light source is used as the light source of the illuminationoptical system, light can be guided through the optical fiber. As aresult, since diffusion of high-intensity light can be suppressed, thelight can be made to propagate with high efficiency. Furthermore, sincethe coaxial illumination structure in which the white light and light ina specific narrow visible wavelength band are irradiated from the sameoptical path, it is not necessary to newly provide plural illuminationoptical systems in the insertion portion of the endoscope. Furthermore,since the light guiding path can be formed by the optical fiber, a lightguide of the related art (optical fiber bundle) is not needed.Accordingly, it becomes easy to make the diameter of the endoscopeinsertion portion small.

Moreover, since laser beams from the near-ultraviolet laser light source135 which generates light in a specific narrow visible wavelength bandis invisible light, all of the laser beams are not wavelength-convertedby the second wavelength conversion member. Accordingly, even if a partof the laser beams are transmitted through the second wavelengthconversion member, the color balance of illumination light emitted isnot affected. As a result, the diagnostic precision of the endoscope canbe maintained high without causing a color change in an observed imagewithin the body cavity. In addition, the near-ultraviolet laser beamsfrom the near-ultraviolet laser light source 135 are hardly absorbed bythe first wavelength conversion member. Accordingly, since a drop inlight intensity is small, an illumination optical system with high lightuse efficiency can be built.

A wavelength band of excitation light of the above-described secondwavelength conversion member is preferably set so that the fullbandwidth at half maximum is 40 nm or less. This is based on thefollowing reasons. An imaging device, such as a CCD or a CMOS, has acolor filter. For example, full-color image information is generated bysetting primary colors (also including the combination of cyan, magenta,and yellow as complementary colors) of R (red), G (green), and B (blue)as specific detection colors. In light intensity detection of eachdetection color, the light intensity in an effective sensitivitywavelength band of a certain wavelength width is detected. However,since wavelengths of the respective detection colors are practicallyclose to each other, parts of the effective sensitivity wavelength bandsoverlap each other. Color mixture occurs, if there are many overlapregions. Therefore, the overlap regions are usually made narrow.

The effective sensitivity wavelength band is designed to 100 nm or lessin B, to 80 nm or less in U, and to 100 nm or less in R in order toprevent color mixture with G (in this specification, this is called a“substantial effective sensitivity wavelength band”). Therefore, inorder to detect each detection color with no influence of color mixturein an imaging device, it is preferable that a wavelength band ofexcitation light is smaller than the substantial effective sensitivitywavelength band. In other words, a full width of an emission spectrumcurve of a specific visible wavelength band in which the wavelengthconversion member 145 is excited to emit light, at half maximum thereof,is smaller than a full width of a spectral sensitivity curve of awavelength band in which a specific detection color of a color filter isdetected, at half maximum thereof. Accordingly, excitation light in aspecific wavelength band is not detected any more over plural effectivesensitivity wavelength bands. Moreover, according to a body to beinspected to be observed, the center of the spectrum may be shifted fromthe center of a color filter. In this case, it is necessary to makenarrower the width of the wavelength band of excitation light.

For this reason, the width of the wavelength band of the excitationlight of the second wavelength conversion member 47 is set to 60 nm orless, preferably to 40 nm or less, and more preferably 20 nm or less.Moreover, from the point of view of light intensity, this width ispreferably 10 nm or more. The width of the wavelength band of theexcitation light may be arbitrarily set by appropriately selecting thesecond wavelength conversion member, for example.

Moreover, in addition to the reason of light intensity detection of theimaging device, a point that making a band narrow is needed whenperforming a diagnosis using a narrowband endoscope (narrowband imaging:NBI) will also be described. When illumination light is irradiated to aliving body tissue, the light propagates while diffusing. If absorptionor scattering property is strong, the light is observed as reflectedlight without propagating deeply into the living body tissue. Theabsorption and scattering properties have strong wavelength dependency.The shorter the wavelength, the stronger the scattering property.Accordingly, the invasion depth of the living body tissue at which lightcan arrive is determined by the wavelength of light irradiated.Particularly, for observation of a microstructure of a mucous surfacewhich is important for early diagnosis of a disease, information from ashallow layer from the surface is important. In this case, informationfrom a layer to be observed can be selectively extracted by setting awavelength band of excitation light of the second wavelength conversionmember to a desired wavelength and making the wavelength band narrow.

As described above, according to the endoscope apparatus of thisembodiment, either the white light, which is formed including a laserbeam and light emitted by excitation of a phosphor, or light in aspecific narrow visible wavelength band can be selectively irradiatedwith the simple configuration while making the diameter small. Inaddition, the light source device and the endoscope apparatus using thelight source device are not limited to this embodiment described abovebut may be suitably changed or modified. For example, theuser-friendliness can be improved by performing free switching betweenwhite light and light in a specific narrow visible wavelength band by aneasy manual operation using a switch provided in the main body operationportion 111 of the endoscope 110.

Fourth Embodiment

Hereinafter, a light source device according to a fourth embodiment, anendoscope apparatus using this light source device, and an imageprocessing method will be described in detail with reference to theaccompanying drawings. FIG. 16 is a view illustrating the conceptualconfiguration of the endoscope apparatus according to the fourthembodiment. An endoscope apparatus 201 is configured to mainly includean endoscope 210, a light source device 220, an image processing device230, and a monitor 240. The endoscope 210 includes a main body operationportion 211 and an endoscope insertion portion 213 which is provided tobe connected to the main body operation portion 211 and is inserted intoa body to be inspected (body cavity). An imaging device 215 and animaging lens 217 which constitute an imaging optical system are disposedat the tip of the insertion portion 213. Moreover, an illuminationoptical member 219 of an illumination optical system and an opticalfiber 221 connected to the illumination optical member 219 are disposednear the imaging optical system. The optical fiber 221 is connected tothe light source device 220, which will be described in detail later,and an imaging signal from the imaging device 215 is input to the imageprocessing device 230.

An imaging device, such as a CCD or a CMOS, is used as the imagingdevice 215. The imaging signal is converted into image data by animaging signal processing section 227 based on a command from a controlsection 229 and appropriate image processing is performed for the imagedata. The control section 229 outputs the image data output from theimaging signal processing section 227, as an image, to the monitor 240which is an imaged image display unit or distributes informationincluding the image data through a network, such as a LAN (not shown).Moreover, a first memory 251 and a second memory 252 for storing imagingsignals are connected to the control section 229. The first and secondmemories 251 and 252 will be described later.

Next, an example of the configuration of the illumination optical systemwill be described. FIG. 17 is a view illustrating the schematicsectional configuration of the illumination optical system at the tip ofan endoscope insertion portion of the endoscope apparatus shown in FIG.16. The illumination optical system is configured to include a whitelight illumination system 261 for emitting white light and a specificcolor light illumination system 63 for emitting specific color light,such as green light and blue light. The white light illumination system261 includes an excitation light source section 265 having a blue laserlight source (first light source) 233 having a center wavelength of 445nm and a condensing lens 241 for condensing a laser beam from the bluelaser light source 233. The illumination optical member 219 disposed atthe tip of the endoscope insertion portion 213 is formed by a wavelengthconversion member 245 which converts a laser beam into visible light.Moreover, the excitation light source section 265 and the illuminationoptical member 219 are connected to each other by the optical fiber 221.

The blue laser light source 233 emits a blue laser beam whilecontrolling the amount of emitted light based on a command from a whitelight driving section 267. The emitted light is irradiated to thewavelength conversion member 245 of the endoscope insertion portion 213through the optical fiber 221. The wavelength conversion member 245 isconfigured to include plural types of phosphors (for example, aYAG-based phosphor or a phosphor including BAM (BaMgAl₁₀O₃₇)) whichabsorb a part of the laser beam from the blue laser light source 233 andare excited to emit light of green to yellow. Then, the laser beam fromthe blue laser light source 233 and the excitation light of green toyellow converted from the laser beams are mixed to generate white light.

As the blue laser light source 233, a broad area type InGaN laser diodemay be used. Moreover, the optical fiber 221 is inserted into a hole 213a formed in a front-end hard portion (metal block) of the endoscopeinsertion portion 213 and is fixed to a fixing jig 275, which is fit andfixed to the hole 213 a, along the optical axis. The fixing jig 275fixes the wavelength conversion member 245 at the light emission side ofthe optical fiber 221, and receives emitted light from the optical fiber221 and emits light, which emitted by excitation of the wavelengthconversion member 245, forward on the optical path. At this time, theblue laser beam transmitted through the wavelength conversion member 245without wavelength conversion is diffused by the phosphor in thewavelength conversion member 245 and is emitted as diffused light whichhas a diffusion angle of 60° to 70° with respect to the optical axisfrom a laser beam with high directivity.

On the other hand, a specific color light illumination system 263 usesan LED (light emitting diode) device as a light source and is configuredto include a blue LED device 271 and a green emission LED device 273which are connected to a specific color light driving section 269. Theblue LED device 271 and the green emission LED device 273 arerespectively disposed in receiving seats 213 b and 213 c which areformed to be recessed in the front-end hard portion and whose side wallsare reflective surfaces. Near the receiving seats 213 b and 213 c,electrode pads 277A and 277B are respectively disposed to be connectedto N-type and P-type electrodes of each LED device by wire bonding.Moreover, each of the LED devices 271 and 273, each of the electrodepads 277A and 277B, and a gold wire are molded with a transparent resin.These molded transparent resins 279A and 279B function as lenses.Moreover, they are described as a blue LED and a green LED. However,since the luminous efficiency of the green LED is low, a 405 nm purpleLED may be used, for example, by mixing a phosphor which emits greenlight, dye, or pigment in a transparent resin. Similarly, a 375 nmultraviolet LED and a phosphor which emits purple-blue light may bemixed in a resin and be sealed.

The specific color light driving section 269 separately controls theamount of light emitted from the blue LED device 271 and the greenemission LED device 273. The specific color light driving section 269 iscontrolled together with the white light driving section 267 by thecontrol section 229 (FIG. 17). The white light driving section 267, thespecific color light driving section 269, and the control section 229function as an illumination light control unit that performs switchingof illumination light and the like. With the above-describedconfiguration, the blue laser beam from the blue laser light source 233emitted from the optical fiber 221 is irradiated to the wavelengthconversion member 245, and the wavelength conversion member 245 absorbsa part of the blue laser beam and is excited to emit light (light ofgreen to yellow) which has a longer wavelength than the blue laser beam.

FIG. 18 is a graph illustrating the spectrum distribution of light aftera blue laser beam is wavelength-converted by the wavelength conversionmember 245. The blue laser beam from the blue laser light source 233 isexpressed by an emission line having a center wavelength of 445 nm.Light emitted from the wavelength conversion member 245 excited by thelaser beam increases the emission intensity in a wavelength band ofapproximately 450 nm to 700 nm White light is formed by light within thewavelength band and the blue laser beam.

FIG. 18 is emission spectrums of the blue LED device 271 and the greenemission LED device 273 of the specific color light illumination system263. The emission spectrum obtained by the blue LED device 271 is lighthaving a narrow wavelength band of about 450 to 480 nm at half maximumthereof, and the emission spectrum obtained by the green emission LEDdevice 273 is light having a narrow wavelength band of about 520 to 560nm at half maximum thereof.

Next, an example of the use of the endoscope apparatus 201 when thelight source device 220 having the above-described configuration isbuilt into the endoscope 210 will be described. As shown in FIG. 17, inthe endoscope apparatus 201, the endoscope insertion portion 213 isinserted into a body cavity, white illumination light is illuminatedthrough the illumination optical member 219 from the tip of theendoscope insertion portion 213, and the illumination light by specificcolor light is emitted from each of the LED devices 271 and 273. Thewhite light and the specific color light are switched so that only oneof them is emitted. In addition, reflected light after the emitted lightis irradiated to the body to be inspected is imaged through the imaginglens 217 in the imaging device 215. An imaging signal obtained byimaging is output to the monitor 240 after being subjected toappropriate image processing by the imaging signal processing section227. Or the imaging signal is stored in a recording medium.

In case of imaging using this imaging device 215, at the time of normalendoscopic diagnosis in which observation is performed by irradiatingwhite illumination light within the body cavity, the control section 229turns on an output of a laser beam from the blue laser light source 233by the white light driving section 267 shown in FIG. 17 and turns offeach output of the blue LED device 271 and the green emission LED device273 by the specific color light driving section 269. In this case, whiteillumination light generated by the laser beam from the blue laser lightsource 233 and the light emitted by excitation of the wavelengthconversion member 245 is irradiated to the body to be inspected.Moreover, when performing spectral diagnostics by the endoscopeapparatus 201, the control section 229 turns on each output of the blueLED device 271 and the green emission LED device 273 by the specificcolor light driving section 269 and turns off an output of the bluelaser light source 233 by the white light driving section 267. In thiscase, blue light and green light having narrow wavelength bands by theblue LED device 271 and the green emission LED device 273 are irradiatedto the body to be inspected. Then, reflected light from the body to beinspected to which the green light and the blue light are illuminatedsimultaneously is imaged by the imaging device 215, and the imagingsignal processing section 227 generates a pseudo color image forspectral diagnostics. For example, the pseudo color image is generatedby converting a green detection signal (reflected light component ofnarrowband green light) obtained by the imaging device 215 into a redcolor tone and converting a blue detection signal into blue and greencolor tones. According to the pseudo color image, a surfacemicrostructure (for example, a microstructure of a capillary vessel or amucous membrane) of a surface layer of a body to be inspected can beclearly observed.

Here, a specific control example of spectral diagnostics will bedescribed. FIG. 19A is a view illustrating plural frame images obtainedin a time-series manner by imaging with the imaging optical system, andFIG. 19B is an explanatory view conceptually illustrating a state wherethese frame images are rearranged and displayed. Here, an observed imageunder illumination light of white light and an observed image underillumination light in a specific visible wavelength band (green, blue)are separately displayed on the monitor 140. As shown in FIG. 19A, thecontrol section 229 controls the light source device 20 to emit the bluelaser beam having the center wavelength of 445 nm in a first frame,thereby irradiating the white light to the body to be inspected. Theimaging device 215 images the body to be inspected illuminated by thewhite light and stores the imaging signal in the first memory 251 (seeFIG. 16).

Then, the control section 229 controls emitted light from the lightsource device 220 to irradiate blue light and green light with narrowwavelength bands, which are obtained by the blue LED device 271 and thegreen emission LED device 273, to the body to be inspected in the secondframe. The imaging device 215 images the body to be inspectedilluminated by the green light and the blue light and stores the imagingsignal in a second memory 253.

Hereinafter, in the same manner as described above, processing ofirradiation (illumination) of light, imaging, and storing of an imagingsignal is repeatedly performed similarly to the first frame in a thirdframe (odd frame) and similarly to the second frame in a fourth frame(even frame). That is, the illumination of the white light and theillumination including light in the specific visible wavelength band arealternately switched every imaging frame of the imaging device 215.Then, as shown in FIG. 19B, the illumination images under the whitelight are accumulated in the first memory 251, and the images fornarrowband diagnosis under the green light and the blue light areaccumulated in the second memory 253. As image information based onthese two types of imaging signals, the imaging signals stored in thefirst and second memories are displayed in different display regions 255and 257 on the monitor 240, like in FIG. 13. Although the sizes of thedisplay regions are set equal in the example shown in FIG. 13, the sizesmay be set arbitrarily. For example, one of the display regions may bedisplayed larger than the other display region, or the other image maybe displayed small within one display region.

Thus, by alternately imaging an image under the illumination of thewhite light and an image under the illumination including the light inthe specific visible wavelength band, both the images can be acquiredapproximately at the same time. Accordingly, two types of imageinformation can be simultaneously displayed in real time. In addition,since the observation position and the property of the observed portioncan be understood simultaneously by displaying the imaged images side byside, the diagnostic precision based on the spectral diagnostics can befurther improved.

Moreover, when performing imaging by irradiating light in a specificvisible wavelength band to perform spectral diagnostics, the combinationof various light components is also available in addition to thecombination of illumination light of the blue light from the blue LEDdevice and the green light from the green emission LED device. A pseudocolor image may also be generated by using a blue laser beam from theblue laser light source 233 for white illumination, for example, asnarrowband specific color light instead of the blue light from the blueLED device 271. The pseudo color image obtained as described above maybecome an image useful for spectral diagnostics since a wavelength bandof emitted light is narrower than that of the LED device.

Main light components, which are included in a screen of a specificdetection color, for each frame image that is imaged in a similar mannerto FIGS. 19A and 19B are shown in FIG. 20. Here, an example where a YAGphosphor is used as a phosphor of the wavelength conversion member 245will be described. In a first frame that is an imaging signal obtainedby imaging based on irradiation of a blue laser beam having the centerwavelength of 445 nm, a blue detection light screen B1 includesobservation light based on illumination light of the blue laser beamhaving the center wavelength of 445 nm from the blue laser light source233, a green detection light screen G1 includes observation light basedon illumination light of green fluorescent light by the YAG phosphor ofthe wavelength conversion member 245, and a red detection light screenR1 includes observation light based on illumination light of redfluorescent light by the YAG phosphor of the wavelength conversionmember 245.

Then, in a second frame that is an imaging signal obtained by imagingbased on emission of the blue LED device 271 and the green emission LEDdevice 273, a blue detection light screen B2 includes observation lightbased on illumination light from the blue LED device 271, and a greendetection light screen G2 includes observation light based onillumination light from the green emission LED device 273.

Here, when an observed image obtained by white light is considered, thewhite light used for illumination becomes a different color tone fromthat is actually seen if a wavelength component in a specific narrowrange becomes strong. Accordingly, it is ideally desirable to performillumination with light having a spectrum in which a visible wavelengthband is relatively flat. However, as for white illumination in thisconfiguration, the blue laser beam as an emission line is used for whiteillumination. Accordingly, if this is replaced with emitted light fromthe blue LED device 271 having a larger wavelength width than a laserbeam, the spectrum of illumination light can be made flatter. That is,at the time of white illumination, it can improve the color renderingproperties to use blue light having a relatively large wavelengthbandwidth from the LED device in the second frame rather thanillumination light in which a laser beam as an emission line componentis mixed. Thus, an observation light image based on the white light,which has better color rendering properties, can be obtained bycombining G1 and R1 of the first frame with B2 of the second framewithout using the first frame as the observation light image based onwhite light.

Moreover, as an observation light image obtained by narrowbandillumination light, observation light by the blue laser beam obtained onB1 and observation light by narrowband light obtained by emission of thegreen emission LED device 273 obtained on G2 may be combined, and thismay be used as an image for emphasizing process. In this case, since thewavelength width of blue light is small, a tissue surface layer to beobserved can be limited to a shallower region at the surface side.

In addition, it is also possible to adopt the configuration where whiteillumination light and light in a specific narrow visible wavelengthband can be freely switched by an easy manual operation using a switch212 provided in the main body operation portion 211 of the endoscope210. In this case, since illumination light can be switched at arbitrarytiming manually, the user-friendliness can be improved.

As described above, according to the endoscope apparatus 201, thediameter of a light guide needs to be at least about 1 mm or more inorder to guide required light to the tip of the endoscope insertionportion 213 with the light guide. However, in the configuration of usinga single-line optical fiber, the external diameter including aprotective material of an outer coat can be set as small as about 0.3mm. In addition, since the LED device performs illumination by directlyconverting energy into a required wavelength band, light with highefficiency and high illuminance is obtained. Accordingly, as comparedwith the case where light in a narrow wavelength band is extracted byfiltering from a xenon lamp generally used in the endoscope, the samebrightness can be realized with about 1/20 power consumption. Moreover,since exhaust heat can also be reduced, a cooling fan and the like canbe made small and the sound can be reduced. Moreover, since phosphorexcitation light is used as illumination light, superimposition of anoise caused by speckle (interference) and flickering on a dynamicimage, which easily occurs when a laser beam is used as directillumination light, do not occur.

Moreover, according to the configuration of the endoscope apparatus 201,since the heat capacity is reduced due to making the diameter of theendoscope insertion portion 213 small, and heat emission from the LEDdevices 271 and 273 is concerned. However, since the white illuminationlight which requires a relatively large amount of light is supplied byusing a laser beam and the specific illumination light required forspectral diagnostics is supplied by using the LED devices 271 and 273,the amount of heat emission can be suppressed compared with a case wherean LED device is always lighted in high output.

In addition, emitted light from the LED devices 271 and 273 is condensedby lenses formed of the transparent resins 279A and 279B and is thenemitted toward a desired irradiation position. Therefore, as can be seenfrom the relationship between an observation region and a specific colorlight illumination region of FIG. 21, a part of an observation region281 can be set as a specific color light illumination region 283 withoutilluminating the entire observation region 281 of the imaging device 215with the LED devices 271 and 273. By setting the specific color lightillumination region 283 as a narrow region so that selective irradiationcan be performed, the amount of emitted light from the LED devices 271and 273 becomes small. Accordingly, the amount of heat emission can besuppressed.

Next, a modification of the endoscope apparatus 201 with the aboveconfiguration will be described.

First Modification

FIG. 22 is a view illustrating another sectional configuration of anendoscope insertion portion. In addition to the case where the receivingseats of the LED devices 271 and 273 formed in the endoscope insertionportion 213 of the endoscope apparatus 201 are respectively provided inthe LED devices 271 and 273, the plural LED devices 271 and 273 may alsobe disposed in one receiving seat 213 d. In this case, since the pluralof LED devices 271 and 273 can be collectively molded by a transparentresin 279C, it is possible to simplify a manufacturing process. Inaddition, since the LED devices 271 and 273 share one condensing lens,irradiation unevenness of emitted light can be suppressed.

Second Modification

FIG. 23 is a view illustrating the configuration of another opticalsystem of a light source device. LED devices in this case are the blueLED devices 271 and 273 (either one are provided in parallel to adirection perpendicular to the plane of the drawing) and an infrared(780 nm) emission LED device 276. The LED devices 271, 273, and 274 aredisposed in the same receiving seat 213 e and are molded with atransparent resin 279D. The blue LED device 271, the green emission LEDdevice 273, and the infrared emission LED device 274 are all connectedto the specific color light driving section 269 and the emission stateis controlled.

FIG. 24 is emission spectrums of the blue LED device 271, the greenemission LED device 273, and the infrared emission LED device 274 in thecase. According to this configuration, not only blue light to greenlight used for spectral diagnostics but also infrared light can beemitted. Accordingly, for example, a medical examination based oninfrared light observation becomes possible. The infrared lightobservation is a technique of highlighting a blood vessel or hyperplasiaof a deep portion of a mucous membrane, which is difficult to be seen tohuman eyes, by performing intravenous injection of ICG (indocyaninegreen) in which infrared light is easily absorbed and then irradiatinginfrared light. Moreover, blood flow information may also be displayed.

In each endoscope apparatus described above, for light with a narrowwavelength band used for spectral diagnostics or the like, that is, foremitted light of the blue LED device 271 and the green emission LEDdevice 273, the wavelength band is preferably set to 40 nm or less inhalf bandwidth.

Fifth Embodiment

FIG. 25 is a schematic sectional view illustrating an endoscopeapparatus that uses a light source device according to a fifthembodiment. FIG. 26 is a schematic view illustrating details of thelight source device according to the fifth embodiment used in theendoscope apparatus shown in FIG. 25. An endoscope apparatus 310 shownin FIG. 25 has an endoscope 312 and a control device 314. FIG. 25 showsthe schematic sectional view of the endoscope 312, and also shows thearrangement of an optical system in the endoscope 312 and an opticalpath. The endoscope 312 is a so-called electronic endoscope which has asmall television camera (CCD) built on the tip and transmits acquiredimage information as an electric signal to the control device 314.

The endoscope 312 is configured to include: an insertion portion 316inserted into the body; an operation portion 318 for performing an angleoperation of the tip of the insertion portion 316 and operations such assuction, gas delivery, and water delivery from the tip of the insertionportion 316; a connector portion 322 for connecting the endoscope 312 tothe control device 314; and a main body operation portion 320 thatconnects the operation portion 318 with the connector portion 322. Inaddition, the scale of the endoscope 312 in FIG. 25 is adjusted so as tofacilitate understanding and is different from the actual scale. Forexample, in practice, the insertion portion 316 is very thin as comparedwith other portions and has a length sufficient to reach a part to beobserved. Moreover, although not shown, a forceps channel for insertingan instrument for tissue extraction, channels for gas delivery and waterdelivery, and the like are provided in the endoscope 312 in addition tothe image optical system.

The insertion portion 316 is configured to include a flexible softportion 324, an angle portion 326, and a tip portion 328. An irradiationport 330 through which light is irradiated to the part to be observed,an imaging device (CCD) 332 for acquiring image information of theobserved part, and an objective lens (not shown) are provided in the tipportion 328. The angle portion 326 is provided between the soft portion324 and the tip portion 328 and is bent by a wire operation from theoperation portion 318, an actuation operation of an actuator, and thelike. The angle portion 326 can be bent in an arbitrary angle setaccording to a part for which the endoscope 312 is used, for example, 0°to 210° upward, 0° to 90° downward, 0° to 100° leftward, and 0° to 100°rightward. By bending the angle portion 326, the irradiation port 330and the imaging device 332 of the tip portion 328 can be made to face atarget position to be observed. The minimum bending radius of the angleportion 326 is set to R7.5 mm, for example.

The control device 314 has: a blue laser diode (hereinafter, referred toas an LD) (B-LD) 334 and an infrared LD 336 (IR-LD), which are twosemiconductor laser light sources (semiconductor light emitting devices)and serve as light sources of excitation light; an optical pathadjusting section 338 for making blue light from the blue LD 334 andinfrared light from the infrared LD 336 be incident onto one opticalfiber 340 (which will be described later); a light source controller 342that controls the blue LD 334 and the infrared LD 336 to emit light in atime-series manner; and a processor 344. The processor 344 converts anelectric signal (imaging signal) transmitted from the endoscope 312 intoa digital image signal (video signal), performs image processing on thedigital image signal, and supplies the digital image signal to an imageoutput device (not shown), such as a television or a monitor.

One optical fiber 340 and one scope cable 346 are inserted inside theendoscope 312, and the imaging device 332 is attached to the tip of thescope cable 346. A base end of the optical fiber 340 is connected to theoptical path adjusting section 338 since the connector portion 322 atthe hand side (base end side) of the endoscope 312 is connected to thecontrol device 314. The optical fiber 340 serves to guide the blue lightfrom the blue LD 334 and the infrared light from the infrared LD 336toward the tip of the endoscope 312 through the optical path adjustingsection 338. The optical fiber 340 is inserted in the endoscope 312. Oneend (base end) of the optical fiber 340 is connected to the optical pathadjusting section 338 of the control device 314, and the other end (tip)extends from the connector portion 322 of the endoscope 312 to the tipportion 328 of the insertion portion 316 through the main body operationportion 320.

Near the irradiation port 330 of the tip portion 328 of the insertionportion 316 of the endoscope 312, a phosphor portion 348 (an example ofa wavelength conversion member) which is covered with one or morephosphors or includes one or more phosphors is disposed with beingattached to the tip of the optical fiber 340. In the tip portion 328 ofthe endoscope 312, the tip of the optical fiber 340 extends to theposition of the phosphor portion 348. Accordingly, the blue light fromthe blue LD 334 is incident on the phosphor portion 348 and is thenemitted from the irradiation port 330 as white light (or pseudo whitelight) that becomes illumination light. Also, the infrared light fromthe infrared LD 336 is incident on the phosphor portion 348, istransmitted through the phosphor portion 348 as it is, preferably,without being absorbed by the phosphor portion 348 and without beingsubject to the wavelength conversion, and is emitted from theirradiation port 330. Moreover, the scope cable 346 is a cable fortransmission of an imaging signal. Since the connector portion 322 ofthe endoscope 312 is connected to the control device 314, one end (baseend) thereof is connected to the processor 344, and the other end (tip)thereof is connected to the imaging device 332. Image informationacquired by the imaging device 332 is transmitted to the processor 344through the scope cable 346 and is subjected to image processing. Then,the image information is converted into certain display imageinformation and is displayed on an image output device (not shown), suchas a television or a monitor.

In this embodiment, the blue excitation light which is emitted from theblue LD 334 and is then incident on the optical fiber 340 through theoptical path adjusting section 338 is transmitted to the phosphorportion 348 through the optical fiber 340 so as to excite the phosphorportion 348. The phosphor portion 348 converts a part of the blueexcitation light into fluorescent light having a different wavelengthfrom the blue excitation light and emits the fluorescent light whilemaking the remaining excitation light transmit therethrough. Thefluorescent light and the excitation light emitted from the phosphorportion 348 are mixed to obtain white illumination light, for example.This white illumination light is emitted from the irradiation port 330and is irradiated to the part to be observed. On the other hand, theinfrared light which is emitted from the infrared LD 336 and is thenincident on the optical fiber 340 through the optical path adjustingsection 338 is transmitted to the phosphor portion 348 through theoptical fiber 340, passes through the phosphor portion 348, is emittedfrom the irradiation port 330, and is irradiated to the part to beobserved.

That is, the blue excitation light and the infrared light emitted fromthe blue LD 334 and the infrared LD 336, respectively, are incident onthe optical fiber 340 along the optical path through the optical pathadjusting section 338, are guided by the optical fiber 340, and areintroduced into the phosphor portion 348. The blue excitation lightintroduced into the phosphor portion 348 excites the phosphor of thephosphor portion 348 to be converted into white (or pseudo white) lightand is then emitted as white (or pseudo white) light from theirradiation port 330. The infrared light introduced into the phosphorportion 348 is transmitted through the phosphor portion 348 as it is ifpossible, preferably, without being absorbed by the phosphor portion 348and without being subject to the wavelength conversion, and is emittedas infrared light from the irradiation port 330. Here, the blue LD 334,the infrared LD 336, the optical path adjusting section 338, the opticalfiber 340, the light source controller 342, and the phosphor portion 348constitute the light source device 350 of this embodiment.

Here, FIG. 26 shows details of the light source device 350 of thisembodiment used in the endoscope apparatus 310 shown in FIG. 25. Asshown in FIG. 26, the light source device 350 includes: the blue LD 334which emits the blue excitation light; the infrared LD 336 which emitsthe infrared light in a direction perpendicular to the emissiondirection of the blue excitation light; a dichroic mirror 352 which isdisposed at a position where the blue excitation light from the blue LD334 and the infrared light from the infrared LD 336 cross each other andwhich allows the blue excitation light to transmit therethrough andcauses the infrared light to be reflected toward a directionperpendicular thereto so that an optical path of the infrared light ismade to match an optical path of the blue excitation light; collimatorlenses 354 a, 354 b disposed between the dichroic mirror 352 and theblue LD 334, the infrared LD 336, respectively; the optical fiber 340 anincidence end of which is disposed on an extending line of one matchedoptical path of the infrared light and the blue excitation light; acondensing lens 355 disposed between the dichroic mirror 352 and theoptical fiber 340; a holding end portion 356 which holds a tip portionof the optical fiber 340; and the phosphor portion 348 attached to thetip of the optical fiber 340 held by the holding end portion 356. Here,the blue LD 334, the infrared LD 336, the optical path adjusting section338, and the light source controller 342 constitute the light sourcesection 351.

Here, the dichroic mirror 352, the collimator lenses 354 a and 354 b,and the condensing lens 355 constitute the optical path adjustingsection 338. Also, the holding end portion 356, which holds the tip ofthe optical fiber 340, and the phosphor portion 348 constitute anillumination optical member 358. In addition, the blue LD 334 is anexample of a first light emitting device, and the blue excitation lightis an example of excitation light having a first wavelength. Inaddition, the infrared LD 336 is an example of a second light emittingdevice, and the infrared light is an example of light having a secondwavelength different from the first wavelength of the blue excitationlight. In addition, the illumination optical member 358 is an example ofa third light emitting device, and the white light or the pseudo whitelight is an example of first fluorescent light which is obtained bywavelength conversion in the phosphor portion 348 excited by blueexcitation light, which is emitted from the phosphor portion 348 m andwhich has a different emission wavelength from the first wavelength.

As the blue LD 334, for example, a semiconductor blue laser light sourcehaving a wavelength of 445 nm may be used. As a phosphor of the phosphorportion 348, for example, a YAG (YAG:Ce) (fluorescence wavelength of 530to 580 nm) based yellow phosphor or α-SiALON and CaAlSiN₃ which emitslight in a red region may be used. When a phosphor of the phosphorportion 348 is excited by blue light from the semiconductor laser lightsource as excitation light, fluorescent light ranging from yellow to redor fluorescent light ranging from red to green converted by the phosphorof the phosphor portion 348 and blue excitation light transmittedthrough the phosphor portion 348 are emitted from the phosphor portion348. By mixing of the two types of light, white emission can be obtainedfrom the irradiation port 330. On the other hand, for example, asemiconductor laser light source having a wavelength of 785 nm may beused as the infrared LD 336. Infrared light from such a semiconductorlaser light source seldom excites the phosphor of the phosphor portion348. Accordingly, the amount of fluorescent light converted by thephosphor of the phosphor portion 348 is small, and the most part of theinfrared light transmits through the phosphor portion 348. That is, inthe case of using YAG (YAG:Ce²) as a phosphor in this embodiment, lightis almost not absorbed when a wavelength exceeds 520 nm, such that thephosphor does not emit light. Moreover, the phosphor does not emit lightat all if the wavelength of the light source is in the long wavelengthside (exceeding 550 nm) in the emission spectrum.

In this embodiment, a purple-blue to blue semiconductor laser lightsource having a wavelength of 400 to 550 nm, preferably 400 to 500 nmmay be used as the blue LD 334. Moreover, in this embodiment, a red toinfrared semiconductor laser light source having a wavelength of 630 nmor more, preferably 630 to 800 nm, more preferably 650 to 800 nm may beused as the infrared LD 336. Moreover, in this embodiment, a blue lightexcitation green-yellow phosphor (Ca, Sr, Ba)₂SiO₄:Eu²⁺ (fluorescencewavelength of 500 to 580 nm), SrGa₂S₄:Eu²⁺, α-SiALON:Eu²⁺,Ca₃Sc₂Si₃O₁₂:Ce³⁺, a blue light excitation red phosphor (Ca, Sr,Ba)₂Si₅N₈:Eu²⁺, CaAlSiN₃:Eu²⁺, and the like may be used as a phosphor ofthe phosphor portion 348.

In this embodiment, an energy of fluorescent light (an example of secondfluorescent light) which is emitted from the phosphor portion 348 due toexcitation by infrared light having a certain energy is 1/10 or less,preferably 1/100 or less, more preferably 1/10,000 or less of an energyof fluorescent light (an example of first fluorescent light) which isemitted from the phosphor portion 348 due to excitation by blueexcitation light having the certain energy. FIG. 35A schematically showsan emission spectrum of fluoroaluminum silicate glass doped with Yb andEr when it is excited by light having 445 nm in wavelength, and FIG. 35Bschematically shows an emission spectrum (center wavelength of 550 nm)of fluoroaluminum silicate glass doped with Yb and Er when it is excitedby light having 980 nm in wavelength. In the example shown in FIGS. 35Aand 35B, it is assumed that the excitation light of 445 nm and theexcitation light of 980 nm have the same energy. Since 445 nm (anexample of blue excitation light) is in the excitation spectrum offluoroaluminum silicate glass doped with Yb and Er, fluoroaluminumsilicate glass doped with Yb and Er emits fluorescence light having abroad wavelength band as shown in FIG. 35A. On the other hand, whenfluoroaluminum silicate glass doped with Yb and Er is excited by theexcitation light of 980 nm (an example of infrared light), it also emitsfluorescence light having a narrow wavelength band as shown in FIG. 35B.Although the peak of the fluorescence light caused by the excitationlight of 980 nm shown in FIG. 35B is higher than that of thefluorescence light caused by the excitation light of 445 nm shown inFIG. 35A, the band of the fluorescence light caused by the excitationlight of 980 nm is narrower than that of the fluorescence light causedby the excitation light of 445 nm Therefore, in this example, the areadefined by the emission spectrum shown in FIG. 35B and the abscissa axisof FIG. 35B is equal to less than 1/10 of the area defined by theemission spectrum shown in FIG. 35A and the abscissa axis of FIG. 35A.That is, the energy of the fluorescence light of fluoroaluminum silicateglass doped with Yb and Er when it is excited by the light of 980 nm isequal to or less than 1/10 of the energy of the fluorescence light offluoroaluminum silicate glass doped with Yb and Er when it is excited bythe light of 445 nm.

Further preferably, the second fluorescent light is substantiallyneglected as compared with the first fluorescent light. That is, theinfrared light introduced into the phosphor portion 348 passes throughthe phosphor portion 348 to be emitted as it is without being absorbedby the phosphor of the phosphor portion 348 and without being subject tothe wavelength conversion. In addition, the phosphor of the phosphorportion 348 of the illumination optical member 358 is excited by blueexcitation light. Then, the phosphor portion 348 causes the blueexcitation light to be wavelength-converted so as to emit fluorescentlight, which is emitted as white light or pseudo white light. In thiscase, light obtained by mixing of the wavelength-converted fluorescentlight and the blue excitation light may be white light or pseudo whitelight, or the wavelength-converted fluorescent light itself may be thewhite light or pseudo white light.

Here, in consideration of a refractive index difference between thephosphor portion 348 and a fixing resin that forms a part of thephosphor, the phosphor portion 348 is preferably made of a materialwhich is small in absorption and is large in scattering in an infraredregion, so that the effect that the phosphor portion 348 causes light ina red or infrared region to scatter may be additionally achieved. Inthis way, a concave lens for increasing a divergence angle of infraredlight, which is required at the tip of an optical fiber 428 for guidinginfrared light like the light source 440 of the related art shown inFIG. 33, can be made unnecessary. That is, by appropriately selectingphosphor glass, aggregate, a binder, and the like which constitute thephosphor portion 348, a function of expanding the divergence angle oflight as a scatterer for red light or infrared light can be given to thephosphor. This can prevent a phenomenon as an obstacle in imaging, suchas a speckle generated by potential interference, when using asemiconductor laser light source. In addition, one of the preferablefeatures of this embodiment is that the phosphor of the phosphor portion348 can be used as a scatterer when infrared light is caused to passtherethrough.

Furthermore, in this embodiment, the blue LD 334 is used as the firstlight emitting device, the infrared LD 336 is used as the second lightemitting device, and the phosphor portion 348 emitting fluorescentlight, which will be white light, in response to blue excitation lightfrom the blue LD 334 is used as the third light emitting device.However, the invention is not limited thereto. For example, twosemiconductor laser light sources having different wavelengths may beused as the first and second light emitting devices, and the third lightemitting source including the phosphor portion made of a phosphorexcited by excitation light from one of the semiconductor laser lightsources may be used, so that fluorescent light having a differentwavelength from the excitation light can be emitted from the third lightemitting source. Any semiconductor laser light source and any phosphormay be used so long as fluorescent light emitted from the phosphorexcited by light from the other semiconductor laser light source is 1/10or less of fluorescent light from the third light emitting source. Thelight conversion efficiency may be improved by using as the first lightemitting device, for example, a semiconductor laser light source whichis satisfactory in excitation efficiency of a phosphor and emitspurple-blue light having a wavelength of 405 nm. Thus, since the amountof heat emission of the phosphor portion 348 can be suppressed, stablelight emission can be realized. In addition, illumination light of acolor corresponding to the object of observation using the endoscope 312may be obtained by selecting the wavelength of excitation light of asemiconductor laser light source and the physical properties of thephosphor of the phosphor portion 348.

As described above, in case of using YAG (YAG:Ce²⁺) as a phosphor, lightis seldom absorbed if a wavelength of the light exceeds 520 nm, suchthat the phosphor does not emit fluorescence. Moreover, the phosphordoes not emit fluorescence at all if the wavelength of the excitationlight is on the long wavelength side of the emission spectrum (exceeding550 nm). Moreover, assuming that a green SHG laser is guided through theoptical fiber 340, the case where the phosphor 348 exists at the tip andthe case where not phosphor 348 is provided will be compared. In thelatter case, the speckle interference is hardly seen. This is because aspeckle is not generated by refraction, reflection, diffusion, and thelike due to a refractive index difference between the phosphor and aresin or a glass that is used when fixing the phosphor. Since thetransmittance of the green laser at this time exceeds 50 to 60%, it canbe sufficiently used. Undoubtedly, in a longer wavelength than theemission spectrum, there is no absorption by the phosphor. Up to aninfrared wavelength region (˜1500 nm), the fixing resin, for example,epoxy resin or silicon resin and glass causes no problem.

Moreover, in this embodiment, a part of input light components(excitation light) from a light source is wavelength-converted by thephosphor of the phosphor portion 348. However, output light of a desiredcolor suitable for observation may be obtained by selecting a phosphorso that all of the input light components are wavelength-converted. Thatis, in the above example, a phosphor is excited by blue light, a part ofthe blue light component is converted into light of yellow-green andred, and the remaining blue light (transmitted light) is mixed therewithto generate white color as described above. However, in order to furtherincrease the color rendering properties, it is desirable to use two ormore types of phosphors, and to excite phosphors of three colors of RGB,for example, by purple light to ultraviolet light (400 nm or less, forexample, 380 nm or 365 nm). Moreover, by increasing the number of typesof phosphors by adding an orange color to RGB, for example, output lightwith higher color rendering properties can be obtained.

The optical fiber 340 may be a material which can guide both the blueexcitation light and the infrared light efficiently, and may be anoptical fiber having a single core and having the same configuration.FIG. 27 shows a sectional configuration of the optical fiber 340. Theoptical fiber 340 has a core 340 a, a clad 340 b, a hard clad 340 c, apolyimide reinforcement member 340 d, and a Teflon (registeredtrademark) coating 340 e sequentially from the central portion. Forexample, assuming that the diameter of the core 340 a is 200 μm, thatthe thickness of the clad 340 b is 35 μm, that the thickness of the hardclad 340 c is about 5 μm, that the thickness of the polyimidereinforcement member 340 d is 5 to 10 μm, and that the thickness of theTeflon (registered trademark) coating 340 e is about 100 μm, thediameter of the optical fiber 340 becomes about 0.3 to 0.5 mm Thiscorresponds to half or less of the diameter of a light guide of therelated art. If an optical fiber having a single core is used as theoptical fiber 340, the strength can be substantially increased becausethere is no friction between optical fibers unlike the light guide ofthe related art using a bundle of optical fibers. In addition, drop inlight output with time due to damage of the optical fiber that is causedby repeated use can be prevented. Furthermore, it becomes possible tomake the insertion portion 328 of the endoscope 312 significantly thinor to make the bending radius small.

Meanwhile, since the optical fiber 426 which is used in the light sourcedevice 440 of the related art shown in FIG. 33 and which guides blueexcitation light to the phosphor portion 420 disposed at the tip isdedicated to blue excitation light, the blue excitation light can beguided through the optical fiber 426 efficiently, for example, with theefficiency of 90% or more. However, infrared light cannot be transmittedthrough the optical fiber 426. On the other hand, since the opticalfiber 340 shown in FIG. 27 is required to guide both the blue excitationlight and the infrared light, for example, a magnesium oxide is mixed inthe core 340 a as an additive for allowing the infrared light totransmit therethrough. Since the magnesium oxide is mixed, the opticalfiber 340 can guide the blue excitation light only with the efficiencyof 85 to 86%. Accordingly, although the efficiency is decreased alittle, the infrared light can be guided similarly.

In addition, any optical fiber which can guide both blue excitationlight and infrared light may be used as the optical fiber 340 of thisembodiment. In addition, any additive that gives to the optical fiber340 a function of allowing both blue excitation light and infrared lightto transmit through the optical fiber 340 may be used as the additivethat is mixed in the core 340 a of the optical fiber 340 in order toallow infrared light to transmit therethrough.

Then, the dichroic mirror 352 is included in the optical path adjustingsection 338 and serves as a transflective mirror which causes blueexcitation light emitted from the blue LD 334 to transmit therethrough,reflects infrared light emitted from the infrared LD 336 in theperpendicular direction, and matches an optical path of the infraredlight with an optical path of the blue excitation light. In the aboveexample, the dichroic mirror 352 is disposed at the position on anoptical path of the blue excitation light emitted from the blue LD 334,where the blue excitation light from the blue LD 334 and the infraredlight from the infrared LD 336 cross each other. In addition, thedichroic mirror 352 is not limited to one used in the above example, butmay be a mirror which reflects the blue excitation light emitted fromthe blue LD 334, causes the infrared light emitted from the infrared LD336 to transmit therethrough, and matches the optical path of theinfrared light with the optical path of the blue excitation light. Thecollimator lenses 354 a and 354 b are included in the optical pathadjusting section 338 and serve to make blue excitation light from theblue LD 334 and infrared light from the infrared LD 336 condensed on theincidence surface of the dichroic mirror 352. Accordingly, thecollimator lenses 354 a and 354 b are formed of convex lenses. Inaddition, the condensing lens 355 is also included in the optical pathadjusting section 338 and serves to make infrared light and blueexcitation light emitted from the dichroic mirror 352 condensed on theincidence surface of the optical fiber 340. Accordingly, the condensinglens 355 is formed of a convex lens.

The holding end portion 356 is included in the illumination opticalmember 358 and serves to support the tip portion of the optical fiber340 so as to attach the phosphor portion 48 to the tip portion. Theillumination optical member 358 includes the tip portion of the opticalfiber 340, the phosphor portion 48, and the holding end portion 356. Theillumination optical member 358 serves to cause white light to beemitted from the phosphor portion 48 and also cause infrared light to beemitted. In addition, the light source controller 342 serves to controlthe blue LD 334 and the infrared LD 336 to emit light in a time-serialmanner. In the light source device 350 of this embodiment, when the blueLD 334 is turned on, the light reaches the phosphor portion 48 at thetip of the optical fiber 340 through the dichroic mirror 352, thecollimator lenses 354 a and 354 b for condensing the light on theincidence surface of the optical fiber 340, and the condensing lens 355.At this time, white light is obtained by (i) the blue excitation lightand (i) light of yellow to red from the phosphor in the phosphor portion48. If necessary, the infrared LD 336 is turned on to emit infraredlight.

Sixth Embodiment

Next, a sixth embodiment of the invention will be described. FIG. 28 isa schematic sectional view illustrating an endoscope apparatus that usesa light source device according to the sixth embodiment. FIG. 29 is aschematic view illustrating details of the light source device accordingto the sixth embodiment used in the endoscope apparatus shown in FIG.28. FIGS. 30 and 31 are schematic sectional views illustrating a blueLED device and an infrared emission LED device used in the light sourcedevice shown in FIG. 29. An endoscope apparatus 310 a shown in FIG. 28has the same configuration as the endoscope apparatus 310 shown in FIG.25 except that the configuration of a light source section of a controldevice is different and that a phosphor portion is not provided in a tipportion of an endoscope. Accordingly, the same components are denoted bythe same reference numerals, and detailed explanation thereon will beomitted, and different points will be mainly described.

The endoscope apparatus 310 a shown in FIG. 28 has an endoscope 312 aand a control device 314 a. In a tip portion 328 of an insertion portion316 of the endoscope 312 a, a phosphor portion is not provided at thetip of an optical fiber 340, but the tip portion of the optical fiber340 is directly connected to an irradiation port 330 at the tip of thetip portion 328 of the endoscope 312 a. The control device 314 aincludes: a light source section 361 having a light source unit 362 thatemits white light and infrared light and a light source controller 364that performs control so that the white light and the infrared light areemitted in a time-series manner from the light source unit 362; and aprocessor 344. In addition, the light source section 361 including thelight source unit 362 and the light source controller 364 and theoptical fiber 340 form a light source device 360 of this embodiment.

As specifically shown in FIG. 29, the light source unit 362 includes: acommon substrate 366 formed with a recess 365; a blue LED device 370 andan infrared emission LED device 372 fixed to the recess 365 by anadhesive 368; a resin sealing portion 374 which seals the blue LEDdevice 370 and the infrared emission LED device 372, which are providedin the recess 365, in a sealing region with a phosphor-containing resinin which a phosphor is mixed. Here, on a bottom surface side of theinfrared emission LED device 372, a gold layer 369 is formed. The goldlayer 369 is fixed to the recess 365 of the common substrate 366 by theadhesive 368. On upper surfaces of both sides of the recess 365 of thecommon substrate 366, a copper layer 376 serving as a lower electrode isformed with an insulation layer 375 interposed between the copper layer376 and the common substrate 366. Then, a resist layer 377 serving as aninsulation layer is formed on the copper layer 376 so as to be opened tothe copper layer 376, and a copper layer 378 is formed on the resistlayer 377. An n-side electrode 384 serving as a lower electrode of theblue LED device 370 is bonded to the copper layer 376 by a gold wire379, and a P-side electrode 390 serving as upper electrode is bonded tothe copper layer 378 by the gold wire 379. In addition, a P-sideelectrode 391 serving as a lower electrode of the infrared emission LEDdevice 372 is bonded to the copper layer 376 by the gold wire 379, and aP-side electrode 398 serving as upper electrode is bonded to the copperlayer 378 by the gold wire 379.

The mounting area can be reduced by similarly mounting a plural of LEDchips, in the shown example, the blue LED device 370 and the infraredemission LED device 372 in the same place (recess 365) of the commonsubstrate 366 and sealing them with the same resin including a phosphor.In a known device (light source device 460) shown in FIG. 34, themounting area is increased because a blue LED device 468 which uses aphosphor-containing resin and an infrared emission LED device 472 whichdoes not excite a phosphor are separately mounted and sealed. However,by mounting the blue LED device 370 and the infrared emission LED device372 at the same place, the mounting area can be reduced compared withthat in the known device. In addition, the light source controller 364controls the blue LED device 370 and the infrared emission LED device372 to emit light in a time-series manner similar to the light sourcecontroller 342 of the first embodiment.

The blue LED device 370 is an LED light source (semiconductor lightemitting device) serving as an excitation light source and emits blueexcitation light. In addition, the blue LED device 370 is an example ofthe first light emitting device, and the blue excitation light is anexample of excitation light emitted in a first wavelength. As the blueLED device 370, for example, a blue LED light source with a wavelengthof 440 to 460 nm may be used. As a phosphor mixed in a resin of theresin sealing portion 374, for example, a YAG (YAG:Ce) (fluorescencewavelength of 530 to 580 nm) based yellow phosphor may be used. When aphosphor of such a resin sealing portion 374 is excited by using bluelight from such a blue LED light source as excitation light, fluorescentlight of yellow color or ranging from yellow to red colors converted bythe phosphor of the resin sealing portion 374 and blue excitation lighttransmitted through the resin sealing portion 374 are emitted from theresin sealing portion 374. By mixing of the two types of light, whiteemission can be obtained from the irradiation port 330. Accordingly, theblue LED device 370 and the resin sealing portion 374 in which aphosphor is mixed form a blue light excitation white LED.

On the other hand, the infrared emission LED device 372 is an LED lightsource (semiconductor light emitting device) serving as an excitationlight source and emits infrared light. In addition, the infraredemission LED device 372 is an example of the second light emittingdevice, and the infrared light is an example of light emitted in asecond wavelength different from the first wavelength of the blueexcitation light. As the infrared emission LED device 372, for example,an infrared emission LED device light source with a wavelength of 780 nmmay be used. Infrared light emitted from the infrared emission LEDdevice light source seldom excites the phosphor in the resin sealingportion 374. Accordingly, the amount of fluorescent light converted bythe phosphor in the resin sealing portion 374 is small and most of theinfrared light is transmitted through the resin sealing portion 374.

In addition, the resin sealing portion 374 in which a phosphor excitedby blue excitation light from the blue LED device 370 is mixedcorresponds to the third light emitting device, and white light orpseudo white light corresponds to the first fluorescent light which isemitted from the resin sealing portion 374 with a different emissionwavelength from the first wavelength after wavelength conversion in theresin sealing portion 374 excited by blue excitation light. That is, theblue LED device 370 and the resin sealing portion 374 formed of aphosphor-containing resin form a white (or pseudo white) LED, and whitelight (or pseudo white light) is emitted from the resin sealing portion374. Moreover, the infrared emission LED device 372 emits infrared lightand makes the infrared light transmitted through the resin sealingportion 374 so that the infrared light is emitted to the outside.

Similar to the above-described blue LD 334, a known purple-blue to blueLED light source with a wavelength of 400 to 550 nm, preferably 400 to500 nm may be used as the blue LED device 370. Moreover, similar to theabove-described infrared LD 336, a known red to infrared emission LEDdevice light source with a wavelength of 630 nm or more, preferably 630to 800 nm, more preferably 650 to 800 nm may be used as the infraredemission LED device 72. Moreover, similar to the phosphor in thephosphor portion 48, a blue light excitation green-yellow phosphor (Ca,Sr, Ba)₂SiO₄:Eu²⁺ (fluorescence wavelength of 500 to 580 nm),SrGa₂S₄:Eu²⁺, α-SiALON:Eu²⁺, Ca₃Sc₂Si₃O₁₂:Ce³⁺, a blue light excitationred phosphor (Ca, Sr, Ba)₂Si₅N₈:Eu²⁺, CaAlSiN₃:Eu²⁺, and the like may beused as a phosphor mixed in the resin sealing portion 374.

An energy of fluorescent light (an example of second fluorescent light)which is emitted from the resin sealing portion 374 formed of aphosphor-containing resin after excitation by infrared light having acertain energy is 1/10 or less, preferably 1/100 or less, morepreferably 1/10,000 or less of an energy of fluorescent light (anexample of first fluorescent light) which is emitted from the resinsealing portion 374 after excitation by blue excitation light having thecertain energy. Most preferably, the second fluorescent light issubstantially neglected compared with the first fluorescent light. Thatis, most preferably, the infrared light transmitted through the resinsealing portion 374 passes through the resin sealing portion 374 to beemitted as it is without being absorbed by the phosphor of the resinsealing portion 374 and without wavelength conversion. In addition, thephosphor of the resin sealing portion 374 is excited by blue excitationlight. Then, the resin sealing portion 374 makes the blue excitationlight wavelength-converted to emit fluorescent light, which is emittedas white light or pseudo white light. In this case, light obtained bymixing of wavelength-converted fluorescent light and blue excitationlight may be white light or pseudo white light, or thewavelength-converted fluorescent light itself may be the white light orpseudo white light.

Here, in consideration of a refractive index difference between theresin sealing portion 374 and a resin for fixing and solidification thatforms a phosphor-containing resin, the resin sealing portion 374 ispreferably formed of a material having a particle diameter, which issmall in absorption and is large in scattering in an infrared regionwith respect to the phosphor itself and a filler, so that the effectthat the resin sealing portion 374 makes light in a red or infraredregion scatter may be added. In this way, the infrared emission LEDdevice 472 which emits infrared light does not need to be separated fromthe blue LED device 468 which emits blue excitation light and be sealedwith a resin not containing a phosphor unlike the light source device460 shown in FIG. 34. That is, by appropriately selecting phosphorglass, aggregate, a binder, and the like which form thephosphor-containing resin of the resin sealing portion 374, a functionof extending the divergence angle of light as a scatterer for red lightor infrared light can be given to the phosphor. This can prevent aphenomenon as an obstacle in imaging, such as a speckle generated bypotential interference, when using an LED light source. In addition, oneof the features is that the phosphor of the resin sealing portion 374can be used as a scatterer when making infrared light pass therethrough.

Furthermore, although the blue LED device 370 is used as the first lightemitting device, the infrared emission LED device 372 is used as thesecond light emitting device, and the resin sealing portion 374 sealedwith a phosphor-containing resin which emits fluorescent light becomingwhite light by blue excitation light from the blue LED device 370 isused as the third light emitting device in the shown example, theinvention is not limited thereto. For example, two LED light sourceswith different wavelengths may be used as the first and second lightemitting devices and a third light emitting source including a resinsealing section sealed with a phosphor-containing resin excited byexcitation light from one of the LED light sources may be used, so thatfluorescent light with a different wavelength from the excitation lightcan be emitted from the third light emitting source. Any LED lightsource and phosphor-containing resin may be used if fluorescent lightemitted from the resin sealing section sealed with thephosphor-containing resin excited by light from the other LED lightsource is 1/10 or less of fluorescent light from the third lightemitting source. Moreover, as the blue LED device 370, the infraredemission LED device 372, and the phosphor mixed in the resin sealingportion 374, those having the same functions and effects as the blue LD334, the infrared LD 336, and the phosphor within the phosphor portion48 in the first embodiment described above may be used.

Next, the configurations of the blue LED device 370 and the infraredemission LED device 372 will be described with reference to FIGS. 30 and31. As shown in FIG. 30, the blue LED device 370 has a layer structureincluding: a sapphire substrate 380; an aluminum nitride (hereinafter,referred to as AlN) buffer layer 381 formed on the sapphire substrate380; a non-doped gallium nitride (hereinafter, referred to as GaN) layer382 formed on the AlN buffer layer 381; an Si-doped n-type GaN layer 383formed on the non-doped GaN layer 382; an n-side electrode 384 which isformed on a part of the Si-doped n-type GaN layer 383 and serves as alower electrode; a single quantum well layer (GaN/InGaN light emittinglayer/GaN carrier confinement layer) 385 which is formed on the restupper part of the Si-doped n-type GaN layer 383 and is formed bylaminating a GaN quantum well barrier layer, in which suitable amount ofSi and Mg are doped, and an indium gallium nitride (hereinafter,referred to as InGaN) layer which is a light emitting layer; an Mg-dopedp-type AlGaN carrier block layer 386 formed on the single quantum welllayer 385; a p-GaN layer 388 which is formed on the Mg-doped p-typeAlGaN carrier block layer 386 and in which Mg is doped with highconcentration; a p-side ITO electrode layer 389 formed on the p-GaNlayer 388; and a p-side electrode 390 which is formed on the p-side ITOelectrode layer 389 and serves as an upper electrode.

Such a blue (or green) LED 370 can be manufactured by the followingmanufacturing method. First, a sapphire substrate is prepared, andpretreatment on the prepared sapphire substrate is performed. Then,using metal organic chemical vapor deposition (MOCVD), an MN bufferlayer, an Si-doped n-type GaN layer, a GaN quantum well barrier layer inwhich suitable amount of Si and Mg are doped, and an InGaN layer whichis a light emitting layer are laminated, thereby forming a singlequantum well layer. Then, an Mg-doped p-type AlGaN carrier block layerand a p-GaN layer in which Mg is doped with high concentration aregrown. As a result, an LED wafer can be manufactured. Then, activationtreatment of a p-type carrier is executed and photolithography, adeposition process of an ITO layer for electrode formation and a metalelectrode for wire bonding, and an etching process are repeated. As aresult, a normal LED wafer is manufactured. Then, scratching using adiamond scriber is performed between chips for separation of the chipsand cleaving is performed by using breaking equipment, therebycompleting element separation. In this way, the blue (or green) LED 370can be manufactured.

As shown in FIG. 31, the infrared emission LED device 372 has a layerstructure including: a p-side electrode 391 serving as a lowerelectrode; a p-type GaP substrate 392 formed on the p-side electrode391; a Zn-doped p-type AlGaAs carrier block and electrode contact layer(p-AlxGal-xAs layer) 394 bonded onto the p-type GaP substrate 392 withan adhesive layer 393 interposed therebetween; an AlGaAs light emittinglayer (p-AlyGal-yAs light emitting layer) 395 (x>y aluminum composition)which is formed on the Zn-doped p-type AlGaAs carrier block andelectrode contact layer 394 and in which a suitable amount of Mg isdoped; an Si-doped n-type AlGaAs layer (n-AlxGal-xAs layer) 396; ap-side ITO electrode layer 397 formed on the Si-doped n-type AlGaAslayer 396; and a p-side electrode 398 which is formed on the p-side ITOelectrode layer 397 and serves as an upper electrode.

Such an infrared emission LED device 372 can be manufactured as follows.First, a GaAs substrate is prepared. Then, using the metal organicchemical vapor deposition (MOCVD), an Si-doped n-GaAs buffer layer, anSi-doped n-type AlGaAs layer (n-AlxGal-xAs layer), and an AlGaAs lightemitting layer (p-AlyGal-yAs light emitting layer) in which a suitableamount of Mg is doped are laminated and formed on the prepared GaAssubstrate. Then, a Zn-doped p-type AlGaAs carrier block and electrodecontact layer (p-AlxGal-xAs layer) is grown up. Then, a p-side AlGaAslayer (p-AlxGal-xAs layer) and a p-type GaP substrate are bonded to eachother, and the GaAs substrate used for growth of the p-AlxGal-xAs layeris removed. Then, similar to the case of the blue (or green) LED 370, aphotolithography process, an ITO layer forming process, a metalelectrode deposition process, and an etching process are repeated. As aresult, a normal LED wafer is manufactured. Then, scratching using adiamond scriber is performed between chips for separation of the chipsand cleaving is performed by using breaking equipment, therebycompleting element separation. In this way, the infrared emission LEDdevice 372 can be manufactured.

While the light source device and the endoscope using the light sourcedevice have been described in detail, the invention is not limited tothe above embodiments but various improvements and changes may be madewithout departing from the scope and spirit of the invention. Forexample, the light source device of the invention may also be applied tothe following endoscopes and applications other than endoscopes.

1. Endoscope, observation of blood vessel, measurement of blood flow,infrared fluorescence

2. Neurosurgery, orthopedics, otolaryngology, surgical navigation (forexample, surgical navigation such as a product of Medtronic SofamorDanek, Inc.)

3. Observation of blood vessel using infrared rays during operation (forexample, blood vessel observation system using infrared rays duringoperation such as SPY system of NOVADQ)

4. Light source of system for observation of blood vessel of finger andblood flow rate

5. Pharmacokinetic observation system of animal (infrared fluorescence)

6. Measurement of masseteric oxygen state of dentistry and orthodonticdentistry, and determination of false-tooth plastics

The foregoing description of the exemplary embodiments of the inventionhas been provided for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the invention to theprecise forms disclosed. Obviously, many modifications and variationswill be apparent to practitioners skilled in the art. For example, oneskilled in the art would appreciate to combine any of the aboveembodiments with each other as a modification. The exemplary embodimentswere chosen and described in order to explain the principles of theinvention and its practical applications, thereby enabling othersskilled in the art to understand the invention for various embodimentsand with the various modifications as are suited to the particular usecontemplated. It is intended that the scope of the invention be definedby the following claims and their equivalents.

1. An illumination device comprising a light source including a firstlight source that emits light having a first wavelength, a second lightsource that emits light having a second wavelength different from thefirst wavelength, and a third light emitting device that has or iscoated with one or more phosphors which are excited by the light emittedfrom the first light emitting device to emit first fluorescent lighthaving an emission wavelength different from the first wavelength anenergy of fluorescence light of the third light emitting device when theone or more phosphors of the third light emitting device are excited bythe light having the second wavelength and having a certain energy isequal to or less than 1/10 of that of fluorescence light of the thirdlight emitting device when the one or more phosphors of the third lightemitting device are excited by the light having the first wavelength andhaving the certain energy.
 2. The light source device according to claim1, wherein the energy of the fluorescence light of the third lightemitting device when the one or more phosphors of the third lightemitting device are excited by the light having the second wavelengthand having the certain energy is equal to or less than 1/100 of that ofthe fluorescence light of the third light emitting device when the oneor more phosphors of the third light emitting device are excited by thelight having the first wavelength and having the certain energy.
 3. Thelight source device according to claim 2, wherein the energy of thefluorescence light of the third light emitting device when the one ormore phosphors of the third light emitting device are excited by thelight having the second wavelength and having the certain energy isequal to or less than 1/10,000 of that of the fluorescence light of thethird light emitting device when the one or more phosphors of the thirdlight emitting device are excited by the light having the firstwavelength and having the certain energy.
 4. The light source deviceaccording to claim 1, wherein the fluorescence light of the third lightemitting device when the one or more phosphors of the third lightemitting device are excited by the light having the second wavelengthand having the certain energy is substantially negligible as comparedwith the fluorescence light of the third light emitting device when theone or more phosphors of the third light emitting device are excited bythe light having the first wavelength and having the certain energy. 5.The light source device according to claim 1, further comprising: afirst optical fiber that guides first excitation light emitted from thefirst light emitting device, wherein the one or more phosphors of thethird light emitting device are disposed at an emission end of the firstoptical fiber, fluorescent light emitted from the one or more phosphorsexcited by the first excitation light guided by the first optical fiberis mixed in the one or more phosphors of the third light emitting deviceand is then emitted from the third light emitting device, and emissionlight of the second light emitting device is emitted from the thirdlight emitting device through the one or more phosphors of the thirdlight emitting device.
 6. The light source device according to claim 5,further comprising: a second optical fiber that guides the emissionlight of the second light emitting device, wherein the one or morephosphors of the third light emitting device is disposed to bepositioned at an emission end of the second optical fiber, and theemission light of the second light emitting device is guided by thesecond optical fiber and be then emitted from the third light emittingdevice through the one or more phosphors of the third light emittingdevice.
 7. The light source device according to claim 6, wherein thefirst and second optical fibers are the same one optical fiber, the oneoptical fiber guides the first excitation light emitted from the firstlight source device and the emission light of the second light sourcedevice, the one or more phosphors of the third light emitting device isdisposed at the emission end of the one optical fiber, the fluorescentlight emitted from the one or more phosphors excited by the firstexcitation light guided by the one optical fiber is mixed in the one ormore phosphors of the third light emitting device and is then emittedfrom the third light emitting device, and the emission light of thesecond light emitting device may be guided by the one optical fiber andis then emitted from the third light emitting device through the one ormore phosphors of the third light emitting device.
 8. The light sourcedevice according to claim 6, wherein the second optical fiber includes agermanium oxide in a core thereof.
 9. The light source device accordingto claim 7, wherein the one optical fiber includes a germanium oxide ina core thereof.
 10. The light source device according to claim 5, thesecond light emitting device is mounted below the one or more phosphorsof the third light emitting device.
 11. The light source deviceaccording to claim 1, wherein the first and second light emittingdevices are mounted below the one or more phosphors of the third lightemitting device.
 12. The light source device according to claim 1,wherein the second wavelength of the emission light of the second lightemitting device includes a wavelength in an infrared region.
 13. Anendoscope apparatus comprising: the light source device according toclaim 1.